JP3016839B2 - Facsimile machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile apparatus, and more particularly to a facsimile apparatus that performs communication in a G3 error correction mode recommended by CCITT (International Telegraph and Telephone Consultative Committee).

[Prior Art] In the G3 error correction mode of the CCITT recommendation, an image signal is framed in the HDLC format with a predetermined length (256 octets or 64 octets) specified by a procedure signal plus a frame length of control information of 4 octets and transmitted. However, for the last frame, the image report of the last line + RTC
Is less than a predetermined length, it is permitted to transmit in a frame shorter than a normal frame length (a so-called short frame).

For this reason, in the conventional facsimile apparatus, the condition for determining the acceptability of a received frame is only a check using a frame check sequence (FCS), and does not make a determination based on the validity of the frame length.

[Problems to be Solved by the Invention] However, in the above conventional example, since the validity of the reception frame length is not checked, the HD of the transmitter should be used.
If a malfunction occurs in the LC framing circuit, or if the FCS is determined to be correct by mistake when a frame is lost due to line noise, it cannot be detected despite the presence of a frame error. For this reason, in such a case, there is a drawback in that even if all the received frames are correct, an image defect occurs when decoded and printed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a facsimile apparatus configured so that an image signal in an error correction mode can be made more reliable in view of the above points.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a facsimile apparatus having an error correction function, comprising: an inspection unit for inspecting a frame length of a received frame when an image is received in an error correction mode. Control means for performing a retransmission request assuming that an error is detected when the frame length abnormality is detected by the inspection means, wherein the image signal notified by the information of the post message signal transmitted subsequent to the image signal is provided. As a result of the determination based on the number of frames, if the frame in which the abnormal frame length is detected is only the last frame, all the received frames are regarded as good, and the retransmission request by the control unit is not performed. is there.

[Operation] According to the above configuration of the present invention, at the time of receiving an image signal, the validity of the received frame length is checked in addition to the conventional FCS (frame check sequence) check as a determination condition of the received frame. Thus, more accurate communication can be performed.

[Example] Hereinafter, an example of the present invention will be described in detail.

FIG. 1 is a basic block diagram of a facsimile apparatus according to one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a main control unit for controlling the operation of the entire apparatus, which is used for a microprocessor and a program memory.
It is composed of ROM, RAM for work area, etc.

A reading unit 2 includes a CCD image sensor, a document transport mechanism, and the like.

Reference numeral 3 denotes a recording unit including a thermal printer or a laser printer.

Reference numeral 4 denotes a communication control unit including a modem, an NCU (network control device), and the like.

 5 is a telephone.

 Reference numeral 6 denotes a communication line (telephone line).

 Reference numeral 7 denotes an operation input unit including a keyboard and the like.

 Reference numeral 8 denotes a display unit constituted by an LCD or the like.

Reference numeral 20 denotes a received frame flag (Rf), which is a bit map corresponding to the assigned frame number as shown in FIG.

Reference numeral 30 denotes a frame length abnormality detection flag (Ef), which is a bit map corresponding to the assigned frame number as shown in FIG.

Reference numeral 40 denotes a buffer of 64 Kbytes × 2 blocks for ECM (error correction mode) reception, and paper image data obtained by removing an address, an FCD, a control, and a frame number from a correctly received frame is stored in an address corresponding to a frame number. .

At the start of receiving an image signal in the ECM mode, first, all bits of a reception frame flag Rf and a frame length abnormality detection flag Ef are set to 1 and initialization is performed.

Next, at the time of receiving an image signal, each time a regular image frame in the HDLC format is received, the pure image portion is transferred to the corresponding address area in the 64K block based on the frame number, and the corresponding bit of Rf is set to 0. I do. Further, the frame length of the received frame is determined, and if the frame length matches the predetermined frame length, the corresponding bit of Ef is set to 0.

When all the image signals have been received and the return signal (RCP) to the procedure signal has been received, the procedure proceeds to the procedure signal reception and the post message signal (PPS-Q) reception.

Since the total number of frames transmitted by the transmitter is notified by the PPS-Q, the receiver determines whether or not all the transmitted frames have been correctly received. (MCF). Otherwise, a frame retransmission (partial page) request signal (PP
R) to request that frames not received be retransmitted.

FIG. 3 is a schematic flowchart of the reception frame and the quality judgment in this embodiment.

First, in step S1, the total number of frames notified by PPS-Q after an image that is not retransmitted is set in the register N.

In the next step S2, the bitmap pointer P is set to 0, and in step S3, the error frame counter E is set to 0.

In step S4, it is determined whether or not the bit corresponding to the bitmap pointer P of the reception frame flag Rf is 0. If Rf (P) = 1, since the frame has not been received, the process proceeds to step S7, and the error frame counter E is counted up. If Rf (P) = 0,
Proceeding to step S5, it is determined whether or not the bit corresponding to the bitmap pointer P of the frame length abnormality detection flag Ef is 0. If Ef (P) = 0, the frame length is normal, and the process skips step S6 and returns to step
Proceed to S8. If Ef (P) = 1, it is determined in step S6 whether the frame is the last frame. If it is not the last frame, the received frame is not a regular frame.
Count up. If it is the last frame, it may be a short frame, so it is regarded as a regular received frame.

In step S8, the bitmap pointer P is incremented. In step S9, it is determined whether or not the processing up to the last frame has been completed. The loop from step S4 to step S9 is repeated until the processing of the last frame is completed.

When the processing for all the frames is completed, in step S10, the value of the error frame counter E frame is checked. If E = 0, all transmitted frames have been received normally, and if E ≠ 0, there has been a frame error.

[Effects of the Invention] As described above, according to the present invention, the frame length of a received frame is checked, and a frame having an abnormal length is regarded as an error frame and a retransmission request is made, thereby enabling image reception in the error correction mode. Can be made more reliable.

[Brief description of the drawings]

FIG. 1 is a basic block diagram of a facsimile apparatus according to one embodiment of the present invention, FIG. 2 is a diagram showing an example of setting of a configuration bit assignment of a reception frame flag and a flag for detecting a frame length abnormality, and FIG. It is a flowchart which shows the pass / fail judgment logic. DESCRIPTION OF SYMBOLS 1 ... Main control part, 2 ... Reading part, 3 ... Recording part, 4 ... Communication control part, 5 ... Telephone, 6 ... Line, 7 ... Operation input part, 8 ... Display part, 20 …… Reception frame flag, 30… Frame length abnormality detection flag, 40 …… ECM reception buffer.

Claims (1)

(57) [Claims] 1. A facsimile apparatus having an error correction function, comprising: an inspection unit for inspecting a frame length of a received frame when an image is received in an error correction mode;
And control means for making a retransmission request by regarding the frame as an error frame. As a result of the determination based on the number of frames of the image signal notified by the information of the post message signal transmitted subsequent to the image signal, the frame length abnormality is detected. If the received frame is only the last frame, all the received frames are regarded as good, and the control unit does not request retransmission.