Title: Modulator and demodulator (MODEM)
Abstract: A MODEM can shorten the processing time of an interface disposed between a data terminal equipment (DTE) and the MODEM. The MODEM stores an object program of a procedure in a memory and switches an operational mode of the MODEM automatically corresponding to the prescribed procedure thereby executing the procedure corresponding to the current operational mode. The MODEM further comprises a timer which monitors the transits time between a completed procedure and the next procedure, and the MODEM starts the process of a specified operational mode based on a mode-setting-instruction of the procedure as well as monitoring the transitions time by using the timer, and executing a next specified operational mode when the timer times out, thereby allowing the MODEM to perform the various operational mode switches.
Patent Number: 7,006,261 Issued on 02/28/2006 to Mizutani, et al.
| Inventors:
|
Mizutani; Mikio (Tokyo, JP);
Noma; Nobuhiko (Kanagawa, JP);
Katayama; Eizo (Kanagawa, JP);
Takagi; Genzo (Saitama, JP);
Noguchi; Yoshihiro (Kanagawa, JP);
Araki; Mitsuhiro (Kanagawa, JP)
|
| Assignee:
|
Panasonic Communications Co., Ltd. (Fukuoka, JP)
|
| Appl. No.:
|
458882 |
| Filed:
|
December 10, 1999 |
Foreign Application Priority Data
| Jun 14, 1995[JP] | 7-147235 |
| Jan 11, 1996[JP] | 8-002853 |
| Current U.S. Class: |
358/468; 358/400; 358/404; 375/222 |
| Current Intern'l Class: |
H04N 1/32 (20060101) |
| Field of Search: |
358/400,404,468
379/100.1
375/222
|
References Cited [Referenced By]
U.S. Patent Documents
| 3958088 | May., 1976 | Vieri.
| |
| 5008901 | Apr., 1991 | Wallach et al.
| |
| 5054020 | Oct., 1991 | Meagher.
| |
| 5268928 | Dec., 1993 | Herh et al.
| |
| 5359709 | Oct., 1994 | Blanc et al.
| |
| 5384822 | Jan., 1995 | Brown et al.
| |
| 5450530 | Sep., 1995 | Snyder et al.
| |
| 5657345 | Aug., 1997 | Lazaridis.
| |
| 5711012 | Jan., 1998 | Bottoms et al.
| |
| 5946348 | Aug., 1999 | Mizutani et al.
| |
| 6038252 | Mar., 2000 | Mizutani et al.
| |
| Foreign Patent Documents |
| 0 499 763 | Aug., 1992 | EP.
| |
Other References
WO 92 11593 A, dated Jul. 9, 1992.
Partial European Search Report, (EP 96 30 4413) dated Jan. 15, 2001 (2).
|
Primary Examiner: Wallerson; Mark
Attorney, Agent or Firm: RatnerPrestia
Parent Case Text
This application is a continuation of U.S. patent application Ser. No. 09/107,796,
filed Jun. 30, 1998, which is a continuation of U.S. patent application Ser. No.
08/664,953 filed on Jun. 13, 1996, now U.S. Pat. No. 5,946,348.
Claims
What is claimed is:
1. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures each of which executes successive communication processes, including
a plurality of operational modes, said image data transferred between said memory
means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program in accordance with a predetermined unit of the control procedures, and
control means for executing the control procedure corresponding to the operational
mode just switched.
2. A facsimile apparatus of claim 1, wherein said memory means has a plurality
of areas for storing data from said facsimile controller, said plurality of areas
corresponding to a respective plurality of modes, and when said switching means
switches to one of said plurality of modes, said control means writes the data
corresponding to a further one of said plurality of modes into a different area
of said memory means from the area which stores the data corresponding to a previous mode.
3. A facsimile apparatus according to claim 1, wherein said switching means is
independent from said facsimile controller.
4. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of said plurality of operational modes,
wherein said memory means has a first area for storing a command from said facsimile
controller and a second area for storing data from the facsimile controller in
pairs, each of said pairs corresponding to a respective one of said modes, said
control means is further for transmitting the data stored in said second area of
said memory means to said signal line while inputting a command for storing from
the facsimile controller to the first area corresponding to said second area, and
when completing the transmitting of the data stored in said second area, said control
means determines whether the transmission of the data from said second area is
completed based on the command stored in said first area.
5. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of said plurality of operational modes,
wherein said memory means has a plurality of banks, and also has a respective
plurality of data storage areas for each mode, said plurality of data storage areas
store the data from said facsimile controller in a frame unit into said plurality
of banks.
6. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of said plurality of operational modes,
wherein said memory means has a plurality of banks, a respective plurality of
status areas, wherein said plurality of command areas store information about a
respective plurality of operation instructions, and said plurality of status areas
store information showing a respective plurality of buffer status.
7. A facsimile apparatus of claim 6, wherein the control means provides an error
check of received data from the signal line, and when an error is detected in the
received data, a data-error bit is written into one of said plurality of status
areas, and the received data is deleted from the respective data storage area.
8. A facsimile apparatus of claim 6, wherein the buffer status includes one of
a Data Full/Empty condition, abort condition and error condition.
9. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a control process, said
image data transferred between said memory means and said facsimile controller,
timer means for monitoring a transition time between a completed control process
and a further control process,
means for selecting a control process to be executed in the further control process
during the transition time, and
control means for executing the selected control process when the timer means
times out.
10. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a control procedures, said
image data transferred between said memory means and said facsimile controller,
analysis means for analyzing a received signal,
switching means for switching between a control-channel-mode and main-channel-mode
when said analysis means detects a specified signal, and
control means for executing the control procedure corresponding to the operational
mode just switched.
11. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
analysis means for deframing a received data-frame and analyzing the deframed data-frame,
switching means for switching an operational mode from a main-channel-mode to
a control-channel-mode when said analysis means indicates that the received data-frame
is an RCP (return to control for partial page) frame, and
control means for executing a procedure corresponding to the mode just switched.
12. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
analysis means for analyzing the received signal,
switching means for switching an operational mode from a control-channel-mode
to a main-channel-mode when said analysis means detects a control-channel-ending-signal
comprising a special pattern never occurred during data transmitting, and
control means for executing a procedure corresponding to the mode just switched.
13. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program,
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of said plurality of operational modes,
modulating means for outputting a modulated signal to the signal line,
demodulating means for outputting a demodulated signal from a received signal
fed from the signal line,
error counting means for counting errors of said demodulated signal,
specifying means for specifying an acceptable maximum error volume, and
further control means for controlling said modulating means to transmit a retraining
signal to the signal line when an error volume counted by said error counting means
exceeds said acceptable maximum error volume.
14. A facsimile apparatus of claim 13, wherein said acceptable maximum error
volume is specified by the facsimile controller.
15. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program,
control means for executing a procedure corresponding to the mode just switched,
transmitting means for transmitting a specified signal to the signal line,
timer means for counting a specified time when said transmitting means has started
to transmit the specified signal,
reset means for resetting said timer means when a response signal to said specified
signal is detected from the signal line during the specified time, and
notifying means for notifying the data terminal equipment of an abnormality when
the specified time expires before said response signal is detected from said signal line.
16. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
an interface for sending said image data to and receiving said image data from
the facsimile controller,
an encoder for transducing transmitted data into a first signal,
a modulator for providing a modulation to the first signal,
a hybrid circuit connected to the signal line for separating transmitted signals
and received signals,
a demodulator providing a demodulation to convert one of said received signals
into a second signal,
a judging part for converting said second signal into a third signal,
a decoder for transuding the third signal from said judging part into a further
received data,
an error counter which generates an error-signal by using said second signal
and said third signal,
a calculator for calculating a power of said error-signal, and outputting a quality
signal of the received data, and
a controller for inputting the following three signals:
1. the quality signal of the received data from said calculator,
2. a reference signal for determining a retraining control, said reference signal
selected by the facsimile controller,
3. an identifying signal from said demodulator for identifying said one of said
received signals,
said controller generating a control signal for controlling said modulator.
17. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising: said modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
analysis means for deframing a received data-frame and analyzing the deframed data-frame,
switching means for switching an operational mode from a main-channel-mode to
a control-channel-mode when said analysis means indicates that the received data-frame
is an RCP (return to control for partial page) frame, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of a plurality of operational modes.
18. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
analysis means for analyzing a received signal,
switching means for switching an operational mode from a control-channel-mode
to a main-channel-mode when said analysis means detects a control-channel-ending
signal comprising a special pattern never occurred during data transmitting, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of a plurality of operational modes.
19. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding an image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller,
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures, said image data transferred between said memory means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program,
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of a plurality of operational modes,
transmitting means for transmitting a specified signal to a signal line,
timer means for counting a specified time when said transmitting means has started
to transmit a specified signal,
reset means for resetting said timer means when a response signal to said specified
signal is detected from the signal line during the specified time, and
notifying means for notifying a data terminal equipment of an abnormality when
the specified time expires before said response signal is detected from said signal line.
20. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller;
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures each of which executes a successive communication processes including
a plurality of operational modes, said image data transferred between said memory
means and said facsimile controller,
switching means for switching between a plurality of operational modes responsive
to said object program in accordance with a predetermined unit of the control procedures, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of the plurality of operational modes.
21. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller,
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures each of which executes successive communication processes including
a plurality of operational modes, said image data transferred between said memory
means and said facsimile controller,
analysis means for analyzing a received signal,
switching means for switching between a control-channel-mode and main-channel-mode
when said analysis means detects a specified signal, and
control means for executing the control procedure corresponding to the operational
mode just switched.
22. A facsimile apparatus comprising:
a facsimile controller including
an image reader/recorder for reading/recording an image,
an image data compressor/expander for compressing/expanding image data obtained
from said image,
a console including a control panel for instructing operation of said facsimile controller,
a central processing unit for controlling operation of the facsimile controller,
a modem for transmitting and receiving said image data in modulated form, said
modem comprising:
memory means for storing an object program containing a plurality of control
procedures each of which executes successive communication processes including
a plurality of operational modes, said image data transferred between said memory
means and said facsimile controller,
analysis means for analyzing a received signal,
switching means for switching between a control-channel-mode and main-channel-mode
when said analysis means detects a specified signal, and
control means for executing a respective one of said plurality of control procedures
corresponding to a current one of the plurality of operational modes.
23. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line comprising
the steps of:
deframing a received data-frame from the signal line,
analyzing the deframed data-frame,
switching an operational mode from a main-channel-mode to a control-channel-mode
when said analyzing step detects that the received data-frame is an RCP (return
to control for partial page) frame, and
executing the control procedure corresponding to the operation mode just switched.
24. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line comprising
the steps of:
analyzing the received signal from the signal line,
switching an operational mode from control-channel-mode to a main-channel-mode
when said analyzing step detects a control-channel-ending-signal comprising a special
pattern never occurred during data transmitting, and
executing the control procedure corresponding to the operation mode just switched.
25. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line comprising
the steps of:
switching between a plurality of operational modes responsive to an object program,
executing one of said plurality of control procedures corresponding to one of
said plurality of operational modes switched to,
transmitting a specified signal to the signal line,
counting a specified time with a timer means,
resetting said timer means when a response signal to said specified signals is
detected from the signal line during the specified time, and
notifying the data terminal equipment of an abnormality when the specified time
expires before said response signal is detected from said signal line.
26. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line and storing
an object program containing a plurality of control procedures each of which executes
successive communication processes including a plurality of operational modes comprising
the steps of:
switching between a plurality of operational modes responsive to said object
program in accordance with a predetermined unit of the control procedures, and
executing the control procedure corresponding to the operational mode just switched.
27. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line and storing
an object program containing a plurality of control procedures each of which executes
successive communication processes including a plurality of operational modes comprising
the steps of:
switching between a plurality of operational modes responsive to said object
program in accordance with a predetermined unit of the control procedures, and
executing a respective one of said plurality of control procedures corresponding
to a current one of the plurality of operational modes.
28. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line and storing
an object program containing a plurality of control procedures each of which executes
successive communication processes including a plurality of operational modes comprising
the steps of:
monitoring a transition time between a completed control process and a further
control process with a timer means,
selecting a control process to be executed in the further control process during
the transition time, and
executing the selected control process when the timer means times out.
29. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line and storing
an object program containing a plurality of control procedures each of which executes
successive communication processes including a plurality of operational modes comprising
the steps of:
analyzing a received signal from the signal line,
switching between a control-channel-mode and main-channel-mode when said analyzing
step detects a specified signal, and
executing the control process corresponding to the operational mode just switched.
30. A method for controlling facsimile communication including a modulator and
demodulator for use with a data terminal equipment and a signal line and storing
an object program containing a plurality of control procedures each of which executes
successive communication processes including a plurality of operational modes comprising
the steps of:
analyzing a received signal from a signal line,
switching between a control-channel-mode and main-channel-mode when said analyzing
step detects a specified signal, and
executing a respective one of said plurality of control procedures corresponding
to a current one of the plurality of operational modes.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a MODEM for use with Data Terminal Equipment
(DTE) such as a computer or a facsimile apparatus for data communication via a
telephone line. Specifically, the invention relates to a MODEM which selects an
appropriate modulating method from a plurality of modulating methods.
Description of the Prior Art
Several kinds of modulation methods are available in MODEMs. For example,
frequency modulation, four-phase differential phase shift modulation, quadrature
amplitude modulation, and phase amplitude modulation are available. Selection of
these methods may depend, for example, on the speed of communication. Recently,
many MODEMs, for example a MODEM incorporated in a facsimile apparatus, switch
the modulation/demodulation mode as well as communication speed depending on the
protocol. It is desirable to synchronize the timing of a mode switch between a
transmitter and a receiver. Conventionally, DTE, the host apparatus of a MODEM,
selects an operational mode. The MODEM follows an instruction from the DTE to switch
to the appropriate operational mode.
The DTE is connected to the MODEM via a BUS. The CPU contained within the DTE
distinguishes between transmitted/received data by reading/writing to the transmitting-data-register
and receiving-data-register which are both housed in the MODEM. In addition, the
CPU recognizes the present operational mode of the MODEM by reading the status-register,
and switches the operational mode of the MODEM by writing a mode number into the
mode register. The modulating and demodulating portion of the MODEM follows an
instruction from the mode register, and reports the status of each operation to
the DTE via the status-register.
Before the ITU (International Telecommunication Union) announced the V.34
Standard based on the ITU-T Recommendation, many MODEMs used in facsimile machines
were of the half-duplex type, and timing was not available for transmitting a waveform
simultaneously from the transmitter and receiver. Therefore, either the transmitter
or the receiver transmitted a waveform. The sequence of signal-transmission was
determined by a protocol such as the T.30 Standard.
An operation according to the T.30 Standard is explained below:
If the previous mode is the receive mode, and the content of the received data
is determined to require the next mode to be the transmitting mode, the DTE decodes
the received data and instructs the MODEM to switch the mode. Software processing
in the DTE requires time, however, and produces a signal gap between the end of
the receiving signal and the start of the subsequent transmission. In half duplex
communication the signal gap length will not cause a disruption in communication.
On the other hand, when the communication is based on the full duplex mode of
the V.34 Standard, signals are transmitted simultaneously from both sides by communicating
through a control channel. Accordingly, when the previous mode was the full-duplex
mode of the control channel, and the next mode is to be the receiving mode of a
main channel, the DTE determines the control channel data and gives a mode switching
command to the MODEM. A problem occurs in the above case: The timing of the mode
switch depends on an instruction from the DTE. If processing the transmitted/received
data by the DTE takes time, the MODEM cannot receive the main channel, because
of a delay in switching from receiving of control channel data of the previous
mode to receiving of main channel data of the following mode. When a high speed
MODEM is employed, processing data volume increases, whereby these types of problems
frequently occur.
When a V.34 Standard half-duplex MODEM is used, the main channel of one-way
communication and the control channel of two way simultaneous communication are
alternately switched. In this case, if a signal gap is greater than a specific
period (0.1 seconds), an echo-suppresser is recovered, whereby the control channel
cannot complete the two-way simultaneous communication, and the communication is
unable to recover. In order to prevent this problem, the V.34 Standard specifies
the signal gap to be within 70 ms±5 ms.
Therefore, a mechanism which shortens the processing time is required
in an interface between the MODEM and the DTE. However, if the processing time
can be shortened at the DTE side and switch timing can be accomplished in a shorter
period in proportion to the signal gap length, monitoring the signal gap length
desirably requires approximately ±5 ms accuracy. At the DTE side, software
for monitoring the MODEM status thus desirably requires top priority, whereby the
system design of the DTE becomes difficult.
SUMMARY OF THE INVENTION
The present invention overcomes the problems of the conventional methods, and
shortens the processing time of the interface between the DTE and MODEM as well
as switching operational modes independent of the DTE's software.
According to the present invention, an object program containing the control
procedure is stored in a memory means. Corresponding to the object program execution,
an operational mode is switched automatically in accordance with each procedure
specified in advance. The procedure corresponding to the present operational mode
being switched from the previous mode is automatically executed. In other words,
the MODEM monitors the mode-switch-control and executes mode switching independent
of the host apparatus DTE.
The basic structure of the present invention realizes this feature. Because the
MODEM switches operational modes by itself, the DTE transfer efficiency is increased
and a given timing is guaranteed, whereby data communications which desirably requires
delicate timing can be satisfied, trouble-free communication is secured, and total
communication efficiency is increased.
The present invention has various embodiments for this basic structure. First,
data storage areas which temporarily store the data transmitted to/from the host
apparatus are provided in each operational mode. Accordingly, when the MODEM switches
modes, received data is written into different areas in response to each mode.
If a response speed cannot match the MODEM's communication speed, the received
data of the next mode is stored in another area of the memory means. Therefore,
the received data of the next mode will not overwrite the received data of the
previous frame.
In another embodiment, a data storage area comprises a pair of areas corresponding
to each operation. One area is a command storage area for storing commands from
the data terminal equipment (DTE). The second area is a data storage area for storing
data from the DTE. When data in a storage area is processed, the command written
by the host apparatus into the corresponding command storage area is checked, and
an operation follows the command.
In a further embodiment, the data storage areas of each operational mode have
several banks. The data from the DTE is stored in each bank in a unit called a
frame. An error-check is conducted on the stored data from the DTE. If a data error
is detected, a "data error" is written into a status register, and the received
data which includes the data error is canceled. In this embodiment, the data-error
is not written in the corresponding bank, and the memory capacity is utilized with
greater efficiency. Since the result of the error-check, i.e. data-error, is still
maintained, notice can be given to the DTE that a data-error has occurred.
In another embodiment, the transition time between the end of a procedure and
the start of the next procedure is monitored and a specified operational mode is
automatically started when the transition time exceeds a prescribed period. In
this embodiment, the response-delay to the next mode is prevented where a procedure
requires ±5 ms accuracy for monitoring the signal gap length.
In a different embodiment, a received data frame in the MODEM is disassembled
and analyzed to determine whether the data frame is an return to control for partial
page (RCP) frame. If the data frame is an RCP frame, the operational mode is automatically
switched from the main-channel-receiving-mode to the control channel mode, thereby
preventing the missing of a control-channel-signal arriving within 75 ms after
completing the main channel.
In a separate embodiment, the MODEM analyzes the received data. If the analysis
determines that there is an end signal in the control channel of a pattern which
does not occur in a data transmission, the MODEM automatically switches the operational
mode from the control channel mode to the main-channel-receiving mode, thereby
preventing the missing of a main channel signal arriving within 75 ms after completing
the control channel.
Further, in another separate embodiment, the MODEM calculates an error quantity,
and specifies the acceptable maximum error quantity. When the error quantity exceeds
this acceptable maximum error quantity, a retraining signal is sent to the communication
line. The acceptable maximum error quantity may be controlled by the DTE. Therefore,
in this embodiment, when the quality of received data is lower during data transmission,
the load on the DTE is reduced and also the quality level can quickly be recovered,
whereby the entire communication can end quickly.
Finally, in a separate embodiment a timer is installed. The timer starts
counting a prescribed time simultaneously when the MODEM transmits a specified
signal to the communication line. When a response signal to the specified signal
is detected before the timer reaches the specified time, the timer is reset. Otherwise,
the DTE is informed of an abnormal transmission. In a normal operation where the
response signal is detected from the line, the DTE does not respond to the detection
of the response signal, thereby the DTE processing is never interrupted. Therefore,
the load upon the DTE is reduced when compared to the situation where the DTE is
required to handle transmission line control.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram depicting a MODEM according to an exemplary embodiment
of the present invention.
FIG. 2 depicts a memory structure of a dual port RAM of FIG. 1.
FIG. 3 depicts a memory structure of a channel area used to access a channel
block of an exemplary embodiment of the present invention.
FIG. 4 details a bit map in the channel command illustrated in FIG. 3.
FIG. 5 details a bit map in the channel status illustrated in FIG. 4.
FIG. 6 depicts a relation between command areas, status areas and banks on the
dual port RAM.
FIG. 7 depicts a memory structure detailing a bit map in the command area of
the present invention.
FIG. 8 depicts a memory structure detailing a bit map in the status area in
accordance with an exemplary embodiment of the present invention.
FIG. 9 depicts a memory structure showing a transmission interrupt in accordance
with an exemplary embodiment of the present invention.
FIG. 10 depicts a memory structure showing a receiving interrupt in accordance
with an exemplary embodiment of the present invention.
FIG. 11 depicts a situation of an error-frame being detected when a frame of
received data is checked.
FIG. 12(
a) depicts a conventional memory storing an error-frame after
error detection.
FIG. 12(
b) depicts a memory in accordance with an exemplary embodiment
of the present invention, which cancels an error-frame after error detection.
FIG. 13 depicts when an abort is detected in received data.
FIG. 14(
a) depicts a conventional memory storing an error-frame after
error detection.
FIG. 14(
b) depicts a memory in accordance with an exemplary embodiment
of the present invention, which cancels an error frame after error detection.
FIG. 15 is a control flow chart depicting of a mode switch in accordance with
an exemplary embodiment of the present invention.
FIG. 16 is a receiving side's flow chart depicting a facsimile sequence using
a half duplex mode of the V.34 Standard according to in accordance with an exemplary
embodiment of the present invention.
FIG. 17 depicts a mode switch by RCP detection in accordance with an exemplary
embodiment of the present invention.
FIG. 18 depicts a sample of timing used in facsimile/data communication in the
V.34 mode in accordance with an exemplary embodiment of the present invention.
FIG. 19 depicts a circuit of a MODEM used in accordance with an exemplary embodiment
of the present invention.
FIG. 20 is an internal block diagram of the EQM calculator as shown in FIG.
19. (EQM: eye quality monitor)
FIG. 21 is a flow chart to be executed by the controller as shown in FIG. 19
while in the data receiving mode.
FIG. 22 is a sequence diagram outlining a procedure of the V.34 half duplex
communication mode used in accordance with an exemplary embodiment of the present invention.
DETAILED DESCRIPTION
FIG. 1 is a block diagram outlining a MODEM used in accordance with an exemplary
embodiment of the present invention. A MODEM
11 modulates and demodulates
data. A facsimile controller
12 functions as a host DTE and processes data
expansion and data recording. The MODEM
11 comprises a line controller
111,
an analog front end processor
112 (FEP), a digital signal processor
113
(DSP which digitally processes modulation and demodulation etc., a dual port random
access memory
114 (RAM) having two READ/WRITE access ports, and an interrupt
controller
115.
The facsimile controller
12 comprises an image reader/recorder
123,
an image data compressor/expander
122, a console
121 including a
control panel, a working RAM
124 which temporarily stores image data, and
a central processing unit
125 (CPU) which controls operation of the entire apparatus.
A first access port of the dual port RAM
114 is connected to a BUS B
1
in the MODEM
11, and a second access port is connected to a BUS B
2
in the facsimile controller
12, so that READ/WRITE from the MODEM
11
and facsimile controller
12 can occur simultaneously.
In an exemplary embodiment of the present invention a dual port RAM
114,
is disposed between the DTE and MODEM, in order to increase data transmission efficiency
between the DTE and MODEM as well as reducing the time-load on the DTE software.
The dual port RAM
114 can transmit data in a data-frame unit. The data-frame
unit is an error detecting unit. The buffer area of the frame unit is not limited
to one frame but extends to a block area linking several frames (hereinafter called
as a channel block.)
FIG. 2 depicts a memory structure of the dual port RAM
114 shown in FIG.
1. A communication buffer is independently provided for each mode, such as a channel
block A for the main channel, a channel block B for the transmitter control channel,
a channel block C for the receiver control channel. Each communication buffer has
banks
0-
3. The channel blocks A, B, and C have channel area pointers
(CH area pointer) and channel areas (CH area). The CH area pointers have information
for accessing the CH area.
FIG. 3 depicts a memory structure required for accessing the channel blocks.
A channel command is an area for storing a command. The command switches a corresponding
channel to the transmit mode or the receive mode. A channel status is an area for
displaying the information about an error in transmitting/receiving the corresponding channel.
FIG. 4 details an example of a bit map in the channel command shown in FIG. 3.
FIG. 5 details an example of a bit map in the channel status shown in FIG. 3.
The MODEM
11, structured as above, is explained here when the V.34 half
duplex standard is used in for communication.
This embodiment shows how to control data received from the facsimile controller
12 independent of the operational mode.
When communicating using the V.34 half duplex standard a communication channel
comprises a main channel and a control channel. The main channel is used for image
information in the facsimile communication. The control channel is used for the
communication of Phase B control information recommended in the T.30 Standard of
the ITU-T. The main channel uses channel block A. Channel block B is used for transmitting
the control channel, and channel block C is used for receiving the control channel.
First, the transmission-process of the control channel is described. In phase
B of the T.30 Standard, the MODEM
11 sets the channel mode (bit
7)
of channel block B to a "1" in order to transmit the control channel. Data is written
into the bank
0 of channel block B. The MODEM
11 recognizes the Data
Full/Empty display bit is a "1", confirms the completion of WRITE, reads the data
from Bank
0, processes signals including modulation, and transmits data
to the communication line. After transmitting data from Bank
0, the MODEM
11 changes the Data Full/Empty display bit of Status
0 to "0".
When the Data Full/Empty display bit of Status
1 (which corresponds to
Bank
1) is "0", the facsimile controller
12 writes the next data-frame
into Bank
1 while the MODEM
11 transmits the Bank
0 data.
After completing WRITE, the Data Full/Empty display bit of Status
1 is changed
to "1,". The MODEM
11 checks Status
1 after completing the transmission
of Bank
0. When the Data Full/Empty display bit is "1" (in other words,
the next data-frame was already written), the Bank
1 data is transmitted
the same way as the Bank
0 data was transmitted. Similarly, Banks
2,
3, and
0 are transmitted in this sequence in the data-frame unit.
Although the transmit command of the control channel is being executed, when the
Data Full/Empty display bits of the Bank status in all Banks are "0" and there
is no data-frame available for transmission, the MODEM changes the transmitting-error-display-bit
of channel status B to "1" and information to the facsimile controller
12
of a transmission error in channel block B.
Next, the receiving process of the control channel is described. The MODEM
11 sets the channel mode of channel command C to "0" in order to receive
the control channel. The MODEM
11 receives and demodulates data, confirms
that the Data Full/Empty display bit of Status
0 (which corresponds to Bank
0 of channel block C) is "0", and writes one data frame into Bank
0.
After the writing is completed, the Data Full/Empty display bit of Status
0
is changed to "1" (Completing WRITE=READ Ready.) The facsimile controller
12
confirms that the Data Full/Empty display bit of Status
0 is "1", and reads
data from Bank
0. When the Data Full/Empty display bit of Bank
1
is "0", the MODEM
11 writes the next received data-frame into Bank
1
while the data of Bank
0 is being read by the facsimile controller
12.
Bank
2,
3, and
0, in this sequence, are received and processed
in data-frame units.
Although the receiving command of the control channel is being executed,
when the Data Full/Empty display bits of the Bank status for all Banks are "1"
and received data-frames cannot be written into the vacant banks of C channel block,
the MODEM
11 changes the receiving error display bit of channel status C
to "11", and informs facsimile controller
12 of a receive error of channel
block C As described above, transmitting/receiving of the control channel is processed
by using channel blocks B and C. Therefore, even if the receiving/transmitting
of the control channel is operated in a full-duplex-simultaneous-mode under the
V.34 half duplex Standard, the MODEM and facsimile controller do not require complicated
processes, but can deliver the transmitted/received data of the control channel
securely and efficiently. The transmitting/receiving of the main channel is identical
to that of the control channel. Namely, setting the channel-set-mode-bit of the
channel command in channel block A to "1" switches to the transmit mode, and setting
the channel-set-mode-bit of channel block A at "0" switches to the receive mode.
The transmitting/receiving operation of the main channel can therefore be implemented.
Further in the V.34 half duplex Standard, a mode switch such as between the
transmit/receive operation of the control channel to the transmitting or receive
operation of the main channel, or vice versa can be executed.
Third, the process of stopping the transmission of data is explained by referring
to FIGS. 6-10. FIG. 6 depicts the relationship between the command areas, status
areas and banks on the dual port RAM
114. The command areas store instructions
about operations sent from the DTE such as channel ending, etc. The status areas
store the information about the communication buffer's status such as Data Full/Empty
display, aborts, and errors. These areas are provided to each bank in order to
strictly control the completion of the processes when each bank completes a data
transmission. Each bank stores data in the data-frame unit which is the unit of error-detection.
FIG. 7 details a bit-map in the command area, and FIG. 8 details a bit-map in
the status area. These drawings show the command area and status area corresponding
to Bank
0. This is similarly applied to Banks
1,
2 and
3.
FIG. 9 depicts a memory structure showing a transmit interrupt. FIG. 10 is a memory
structure showing a receive interrupt.
Fourth, an operation of the above structure is explained. With respect to
the data transmission process, e.g. Channel A among several channels is used, the
facsimile controller
12 confirms that the Data Full/Empty display bit of
Status
0 is "0", and writes one transmit data-frame into Bank
0.
When the write is completed, the facsimile controller
12 changes the ending-channel-instruction-bit
to "0" (not end), and changes the Data Full/Empty display bit of Status
0
to "1" (WRITE end ═READ enable).
When the MODEM
11 recognizes that the Command
0 ending-channel
instruction bit is "0" and the Data Full/Empty display bit of Status
0 is
"1", the MODEM
11 reads data from bank
0 to process signals such
as demodulation, and transmits data to line L. When the transmission of the data
from Bank
0 complete, the MODEM
11 changes the Data-Full/Empty display
bit of status
0 to "0" and simultaneously the interrupt controller
115
produces an interrupt to the facsimile controller
12.
The facsimile controller
12 inspects the transmit-interrupt status shown
in FIG. 9, and determines that the MODEM
11 completed the data read from
Bank
0. When the Data Full/Empty display bit of Status
1 is "0",
the facsimile controller
12 writes the next data-frame into Bank
1
while the MODEM
11 transmits the data from Bank
0. After completing
the WRITE, the ending-channel-instruction-bit of Command
1 is changed to
" 1". The MODEM
11 checks Status
1 after completing the transmission
of Bank
0, and when the Data Full/Empty display bit is "1" (in other words,
the next data-frame was already written-in, the Bank
1 data is transmitted
in an identical manner as the Bank
0 data. If there is no ending-channel-instruction,
the MODEM
11 moves to the next bank. Similarly, Bank
2,
3,
and
0, in this sequence, are transmitted in the data-frame unit. When ending
a data transmission (channel A), a data-frame is written into Bank
3 (for
example), the Data Full/Empty display bit of the Bank
3 Status is changed
to "1", and simultaneously the ending-channel-instruction-bit of the Bank
3
Command is changed to "1", thereby giving the MODEM
11 an ending notice.
The MODEM
11 checks the Bank
3 Status and the Bank
3 Command
at the same time, recognizes that both the Data Full/Empty display bit as well
as the ending-channel-instruction bit are "1", thereby completing the data transmission
process after transmitting the Bank
3 data.
Fifth, a data receiving process is explained here. The MODEM
11 demodulates
the received data, and recognizes the Data Full/Empty display bit of Status
0
is "0" and writes one data-frame into Bank
0. When the WRITE is completed,
the MODEM
11 changes the Data Full/Empty display bit of Status
0
to "1" (WRITE end—READ enable.) The interrupt controller
115 produces
an interrupt to the facsimile controller
12.
The facsimile controller
12 inspects the receiving-interrupt-status, and
recognizes that data has been written into Bank
0. When receiving one data-frame,
the MODEM
11 checks whether an abort has occurred, inspects a frame-check-sequence
which is added to the frame-end, and determines whether an error exists. The result
is indicated in the receiving-interrupt-status. After confirming that an abort
did not occur, by inspecting the receiving-interrupt-status, and an error is not
occurring in the data-frame, the facsimile controller
12 reads the data
from Bank
0. When the Data Full/Empty display bit of Bank
0 is "0",
the MODEM
11 writes the next data-frame into Bank
1 while the Bank
0 data is read by the facsimile controller
12. After completing the
WRITE, the data written into Bank
1 is read by the facsimile controller
12, in the same way as the data in Bank
0 was read. In the same manner,
Bank
2,
3 and
0, in this sequence, are processed for receiving
the data-frame unit.
When an error occurs in a data-frame or an abort is detected due to line interference
while receiving data, how to cancel the error frame is explained by referring to
FIG. 11 through FIG. 14. FIG. 11 depicts the status of an error frame detected
when the receiving data-frame is checked. FIG. 12(
a) depicts a memory where
an error-frame is still stored even when the frame has been determined to be an
error-frame. FIG. 12(
b) depicts a memory where an error-frame is canceled
according to this invention.
FIG
