JP2718690B2 - Communication control system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a communication control system, and more particularly, to a communication control device that intervenes between an upper processor and a communication line to control data transmission and reception.

2. Description of the Related Art In a communication control system in which a communication control device is interposed between a host processor and a communication line, and the communication control device performs communication control by sharing with the host processor, the communication control device performs communication control with the host processor. A device for efficiently transmitting and receiving data and control information between devices is required.

In this type of system, for example, as shown in FIG. 7, a plurality of communication control devices 200,.
02 and a main memory 203 are connected by a bus 204, and transmission and reception of data between the host processor 202 and the communication control devices 200 and 201 is performed via the memory 203.

When data is transmitted from the upper processor to the communication line, the transmission data is stored in a predetermined data area of the main memory 203 in a form in which a header (control information) 301 is added before the transmission data 302 as shown in FIG. The processor gives the communication control device a write command that is written and includes the address of the header, so that the communication control device can read the transmission data. When one transmission data (hereinafter, referred to as a frame) cannot be stored in one data area (buffer area) on the memory 203, the frame is divided into a plurality of sub-frames, and each sub-frame is divided into a plurality of sub-frames. Linked by the pointer information in the header (buffer chain). When a plurality of frames are to be continuously transmitted by one communication control device, the plurality of frames are linked by a header (frame chain), and the first frame or the header of a sub-frame is transmitted by a transmission command. Specify an address. As described above, by performing the buffer chain or the frame chain, it is possible to efficiently issue a transmission instruction of long data or a plurality of frames. In the communication control device, the buffer chain provided in the header section
The presence or absence of subsequent data can be determined by the bit BCB or the frame chain bit FCB.

[Problems to be Solved by the Invention] However, in the case of using a command specification capable of transmitting a plurality of frames with one transmission command as described above, the following problems have arisen. In other words, it takes time for the communication control device to finish executing one transmission command, and the upper processor cannot issue the next command. For the same reason, after the upper processor issues one transmission command, other data cannot be sent from the upper processor by an emergency interrupt until the transmission of the communication control device designation data is completed.

Conventionally, for example, JP-A-58-50037 discloses that the contents of the status register of a communication control device are always accessible by a host processor via terminal pins, and commands from the host processor are sent to the communication control device side. There is disclosed a communication control system capable of determining whether or not reception is possible. In this case, when a new command is output from the upper processor during data transmission, the communication control device receives the command once and discards the command.

An object of the present invention is to increase the number of interface terminals between a higher-level processor and a communication control device, and to shorten the next transmission command in a short time after a higher-level processor gives a transmission command of a plurality of frames or a long frame. To provide a communication control system capable of generating the following.

[Means for Solving the Problems] To solve the above problems, the present invention provides a communication control system in which a communication control device sends a transmission frame written to a shared memory by an upper processor to a communication circuit. A transmission control table for registering a transmission control record including the storage address of the transmission frame in the shared memory is provided. In the communication control device, the position of the next transmission control record to be processed on the transmission control table is stored. A first pointer indicating the position of the latest registered transmission control record and a second pointer indicating the position of the latest registered transmission control record. The upper processor registers a transmission frame and a transmission record corresponding to the frame in the shared memory and transmits the transmission frame to the communication control device. When the transmission command is given, the communication control device sets the second
After updating the value of the pointer and providing a completion notification for the transmission command to the upper processor, operating to transmit the transmission frame read from the shared memory based on the first pointer to the communication line, The upper processor can generate a transmission command of another transmission frame after receiving the completion notification.

When the communication control device has a plurality of logical links to the communication line, the transmission control table and the first and second pointers are prepared for each of the logical links. In this case, after registering the transmission control record in any one of the transmission control tables corresponding to the used link, the upper processor generates the transmission command in a form including a parameter for specifying the used link.

[Operation] According to the present invention, upon receiving a transmission command from the host processor, the communication control device, upon updating the second pointer, notifies completion of the transmission command before actual transmission of the transmission frame. To the host processor. Since the period from the issuance of the transmission command to the reception of the completion notification is extremely short regardless of the length of the transmission frame, the upper processor can quickly terminate the execution of each transmission command and immediately issue the subsequent command. You can move on. In the communication control device, the processing of the command from the host processor and the transmission processing of the transmission frame are performed alternately or periodically, and each time the transmission of each frame is completed,
The first pointer is updated. Whether or not a frame to be transmitted exists in the shared memory can be determined by comparing the values of the first and second pointers. Further, the erasure of the already transmitted frame in the shared memory is performed after receiving the acknowledgment from the transmission partner station.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a communication control system according to the present invention, where 200 is a line control device, 202 is a higher-level processor,
Reference numeral 203 denotes a main memory (shared memory) used as a data transfer area between the line control device and a host processor, and these elements are connected by a bus 204. Although a plurality of connections are allowed for the communication control device, only one communication control device is shown in FIG.

The communication control device 200 includes a line control 220 configuring an interface with the communication line 210, an upper interface unit 230 configuring an interface with the upper processor 202, an internal CPU 250, and an instruction (program) executed by the upper internal CPU. It comprises an instruction memory 240 for storing, an internal memory 260 serving as a work memory of the internal CPU, and an internal bus 270 connecting these elements. The upper interface 230 includes a command receiving unit 231 that receives a command from the upper processor, and an upper data transmitting / receiving unit 232 that controls data transmission and reception between the main memory 203 and each element in the communication control device. Upper data transceiver 2
32 preferably has a direct memory access control circuit (DMAC) that executes data transfer independently of the internal CPU 250. In this case, the internal bus 270 is connected between the line control unit 220 and the DMAC. Separately, transmission path 271 and reception path 272
The speed of data transmission / reception processing in the communication control device can be increased by installing the communication control device.

When data is transmitted from the upper processor 202 to the communication line, the transmission data is written to the data buffer area 104 in the main memory 203. As shown in FIG. 2, the data buffer area 104 is composed of a plurality of data blocks of a fixed length, and when the data length of one transmission frame exceeds the data length of one data block, the data of this transmission frame is plural. Is divided into data blocks and written. The address of each data block (buffer address)
The data length is managed by the transmission frame control record 103. When one transmission frame is divided into a plurality of data blocks, each transmission frame control record includes a subsequent control record for managing the address of the next data block and the like in order to specify the next data block. It has a next record pointer to indicate the location.

The transmission frame control record 103 is stored in the transmission control table 102 formed in the main memory. The transmission control table 102 is prepared for the logical link processed by the communication control device 200. If the number of links is l, l transmission control tables 102-1 to 102-1 are prepared.
Each transmission control table, for example, 102-1 stores a transmission frame control record for managing the head data block of each frame for n transmission frames transmitted on the first link. A control record for managing data blocks after the second block in each frame, for example, 103-1 (1) 'in FIG. 2 is stored in a memory area other than the transmission control table 102-1 such as 105. You.

On the other hand, the communication control device 200 stores the number of transmission data equal to the number l of logical links that can be processed by the device in the management table 101.
(101-1 to 101-1) are provided in the internal memory 260. Each management table 101 includes a next transmission frame pointer (NFP) 111 pointing to a control record of a frame to be transmitted next on the transmission control table 102 corresponding to the link,
A latest reception pointer (LFP) 112 pointing to the latest reception control record on the transmission control table is stored.

For example, regarding the first logical link, at the time of initial setting, the next transmission pointer 111 and the latest reception pointer 112 correspond to the first transmission frame control record 103-1 (1) of the transmission control table 102-1 on the corresponding main memory. ). If the value of the next transmission pointer matches the value of the latest reception pointer, it means that there is no frame to be transmitted to the main memory 203 (transmission waiting frame).

When data to be transmitted occurs, the host processor 202
Stores the data in the data buffer area, and sets the address and the data length of the data block in the control record 103-1 (1) which is the latest reception position on the transmission control table 102-1. When data is stored in a plurality of data blocks, the address of the next transmission control record 103-1 (1) 'is stored in the next record pointer of the transmission control record 103-1 (1). If the transmission data can be stored in one transmission data buffer, or if it corresponds to the last linked control record, a specific value, for example, all '0' or all '1' is stored in the next record pointer. Be recorded.

When transmitting a plurality of frames at once, a transmission control record corresponding to the data block at the head of each frame is formed on the transmission control table 102-1.

After the upper processor 202 stores the transmission data and the control information about the transmission data in the data buffer area 104 and the transmission control table 102, the upper processor 202 gives a transmission command to the communication control device 200. For example, as shown in FIG. 3, the transmission command includes a field 301 including a command type (“frame signal”) code,
It comprises a field 302 indicating the number of transmission frames, that is, the number of linked frames, and a field 303 indicating the corresponding link number.

FIG. 6 is a schematic flowchart of a scheduler process executed by the internal CPU 250 of the communication control device 200. In the scheduler process, first, in step 602, various parameters
After initializing the work area and the like, the presence or absence of unprocessed commands, unprocessed received frames, and unprocessed transmitted frames is sequentially checked (steps 610, 620, and 630). A frame reception process (625) and a frame transmission process (635) are executed, and this is repeated.

The transmission command issued by the upper processor is received by the command receiving unit 231 of the communication control device 200. For the transmission command, the consistency of the format and the value indicated in each field is checked. Consistency means, for example: (1) Does the specified link currently exist? (2) Is the sum of the specified number of frames and the number of frames that have received the command and are not currently transmitted less than or equal to the number of fields n in the transmission control table? And so on.

When detecting the inconsistency of these commands, the communication control device notifies the host processor 202 of the fact (such as “command error”) via the command receiving unit 231.
According to the present invention, a normally accepted transmission command is
Processing is performed in the command processing routine 615 as follows.

That is, as shown in FIG. 4, first, the transmission data management table 101 (retained by the number of links) corresponding to the value indicated by the link number field 303 in the command is selected (step 402). The value of the “latest reception pointer” is updated by the “number of transmission frames” indicated by the field 302 in the transmission command (step 404).
In this case, both the next transmission frame pointer and the transmission reception pointer in the transmission data management table 101 represent the control record in the form of the “i-th” or the “j-th” in the transmission control table 102. Shall be. When the above processing is completed, the communication control device notifies the host processor of “completion of command execution” (step 406).

The communication control device can receive the next command at the time when the "command execution end" is notified to the upper processor. According to the present invention, even when a transmission command is issued by chaining a plurality of frames, the time required to execute the flow shown in FIG. 4 does not depend on the number of frames or the length of the frames. The completion of the command processing can be notified to the upper processor in a short time. It should be noted that urgent data, for example, connectionless data that does not refer to or update link state variables (eg, ISDN (Integrated Service
es Digital Network) UI and XID in LAPD protocol
In order to deal with the frame, a table dedicated to emergency data may be provided in the transmission control table 102 in the main memory and the transmission data management table 101 in the communication control device. According to the present invention, since the end of execution from the communication control device is immediately answered, the upper processor 202 can issue the next frame transmission command in a short time, and register the next frame (urgent frame) in the dedicated table. Accordingly, the emergency frame can be transmitted (interrupted) before the frame included in the already-issued transmission command.

FIG. 5 shows a detailed flowchart of the frame transmission processing routine 635. In the frame transmission processing, first, the link to which the frame to be transmitted belongs is determined (step 50).
2). This criterion is (1) that the partner link is not busy, and (2) that the number of outstanding I frames does not reach the maximum number of outstanding I frames. That is, the I frame can be transmitted without receiving a new acknowledgment from the other party.

(3) The selection order is equal to other links or the order of priority is based on a predetermined standard.

When the link is determined, the transmission data management table 101 corresponding to the link is selected, and the value of the next transmission frame pointer and the value of the latest reception pointer are compared (step 506).
If the values match, it indicates that there is no frame to be transmitted on this link, and the next link is selected. If all the links do not satisfy the above conditions and there is no frame to be transmitted, nothing is transmitted and this routine ends (step 504).

If the value of the next transmission frame pointer is different from the value of the latest reception pointer, it means that there is a frame to be transmitted on the link, and the next transmission frame pointer moves from the data buffer area by 1 according to the designated transmission control record. The data for the frame is read and transmitted (step 510), that is, the control record on the transmission control table indicated by the next transmission frame pointer is transferred to the internal memory 260 via the upper data transmission / reception unit, and Data buffer based on buffer address in
The data block from 104 is read, and the contents are transferred to the line control unit 220 via the upper data transmission / reception unit. Internal C
After the PU 250 starts the upper data transmission / reception unit 232 and the line control unit 220, the DMA (Direc
If the data is transmitted using the (t Memory Access) function, the internal CPU can immediately proceed to the next processing. After data transmission for one frame, the next transmission frame pointer is updated by one, and the frame transmission processing routine ends (step 512).

According to the present embodiment, after the upper processor issues the "frame transmission command" and before the frame is actually transmitted, communication of "command execution end" comes from the communication control device. Can issue commands. Even when a plurality of frames are chained and transmission is instructed by a single command, since the execution completion response is received in a short time regardless of the number and length of the chained frames, the upper processor sends the communication processor side. The next processing can be performed without waiting for the processing delay. The main memory 20
3 The transmission frame prepared above is transmitted one by one each time the frame transmission processing routine is executed, and is deleted from the memory after receiving a reception response from the transmission partner station. There is no inconvenience caused by notifying the upper processor of the completion of transmission.

[Effects of the Invention] As described above, according to the present invention, execution (acceptance) of a frame transmission command can be completed in a short time regardless of the presence or absence of a frame chain and the length of each frame. Control of the host processor becomes easy. Further, since the completion response from the communication control device is quick, the processor does not need a dedicated external terminal or the like for detecting the state of each communication control device, so that the system configuration can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a communication control system according to the present invention, FIG.
FIG. 3 is a diagram showing a relationship between a transmission control table and a data block of a transmission frame. FIG. 3 is a diagram showing a format of a transmission command. FIG. A flowchart showing
FIG. 5 is a flowchart showing a frame transmission process, and FIG.
FIG. 7 is a flowchart showing a scheduler process executed by the communication control device, FIG. 7 is a configuration diagram of a conventional communication control system, and FIG. 8 is an explanatory diagram of a frame chain and a buffer chain. 200: Communication control device, 202: Host processor, 203 ...
… Main (shared) memory, 260 …… Internal memory, 101 ……
Transmission data management table, 102 ... Transmission control table, 1
11 first pointer (next transmission frame pointer), 112
... Second pointer (latest reception pointer).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuo Takemura 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Totsuka Plant of Hitachi, Ltd. (72) Inventor Takao Ueno 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan (56) References JP-A-61-253566 (JP, A) JP-A-62-271544 (JP, A)

Claims (2)

(57) [Claims] 1. A communication control device comprising a communication control device between a host processor and a communication line, wherein the communication control device sends a transmission frame written to a shared memory by the host processor to the communication circuit. In the system, a transmission control table for registering a transmission control record including a storage address of the transmission frame in the shared memory is provided, and a transmission control to be processed next on the transmission control table in the communication control device is provided. First indicating the position of the record
A pointer and a second pointer indicating the position of the latest registered transmission control record are provided. The upper processor registers a transmission frame and a transmission record corresponding to the frame in the shared memory, and transmits a transmission command to the communication control device. When given, the communication control device updates the value of the second pointer and gives a completion notification for the transmission command to the upper processor, and then transmits the transmission data read from the shared memory based on the first pointer. A communication control system operable to transmit a frame to the communication line, wherein the upper processor can generate a transmission command of another transmission frame after receiving the completion notification. 2. The communication control device has a plurality of logical links to the communication line, the transmission control table and the first and second pointers are prepared for each of the logical links, and the upper processor is 2. The communication according to claim 1, wherein after registering the transmission control record in any one of the transmission control tables corresponding to the used link, the transmission command is generated in a form including a parameter for specifying the used link. Control system.