JPS5828979B2 - Data frame transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to high-level data link control procedures (H
A data frame transmission method that uses codes to indicate the beginning and end of data, such as DLC), and transmits a series of data with the interval between these codes as one frame.

In this type of conventional data frame transmission method, even if there is a request to send another urgent data frame while a certain data frame is being sent, the transmission cannot be performed until the transmission of the previous data frame is completed, and the current data frame cannot be sent. If the length of the frame being transmitted is very long, subsequent frames have to wait for a long time.

Therefore, in the past, long data and short data, such as facsimile data, were not transmitted over the same line, but were transmitted using separate lines, or long data was transmitted by dividing it into short data frames. I was doing a lot of things.

In order to solve these drawbacks, the present invention provides a data frame transmission system that allows transmission of one data frame by interrupting another data frame while it is being transmitted.

In this invention, frames that can be interrupted during frame transmission, that is, non-priority frames, can be distinguished.

For example, FIG. 1A shows the frame structure of a priority frame, and FIG. 1A shows the frame structure of a non-priority frame.

In these configurations, F indicates the flag sequence of the priority frame, its bit configuration is 8 bits, and its bit pattern is 01111110''.

F indicates a flag sequence of a non-priority frame, and its bit pattern is expressed as a discarded pattern having a pit sequence of seven or more consecutive 'l's.

Whether or not the placement pattern and abandonment pattern are recognized as completely different bit patterns depends on the agreement between the devices.

The F pattern and the next A in the F pattern are address fields consisting of 8 bits, the next C is a control field consisting of 8 bits, and the following ■ is an information field whose bit length is determined by the system regulations. be.

Fe2 following data (2) is a frame check sequence and has a 16-bit configuration.

Note that fields A and (j) can be expanded depending on the system.

FIG. 2 is an example of a transmission control device that implements a function of interrupting and transmitting a priority frame during transmission of a non-priority frame.

Reference numeral 1 designates a control section for controlling a transmission control function, 2 a transmission/reception data buffer section, 8 a character calculation section, 4 an ink face line between the transmission control section 1 and other processing sections, and 5 a frame transmission circuit.

The transmission control function unit 6 is usurped by each of these functions.

The character operation section 3 has the following functions.

That is, in the specific pattern occurrence detection section 80, F
pattern, F pattern, abandonment pattern, and communication termination pattern, and 31 detects the occurrence of the pattern, F pattern, abandonment pattern, and communication end pattern, and 31 transparently transmits frame parts other than these specific patterns, that is, address control information, frame check sequence field,
In other words, in the case of data with consecutive "1"s, a "0" is inserted every five °1"s, and a "0" insertion/removal unit removes the "0"s upon reception. 32 is an Fe2 arithmetic check unit. It is.

Next, an example of the operation of this transmission control device will be explained separately for the transmitting side and the receiving side.

(1) Transmission side ([) After the data link is set up, the control unit 1 manages the state in which information can be transmitted using the state variable rOJ.

In this case, if there is no data to be transmitted, generally the F pattern is transmitted.

(11) When a request for sending a non-priority frame is issued through the interface line 4 when the state variable is rOJ, the control section 1 requests the character calculation section 3 to generate the F pattern and sets the state variable to "2".

After sending the F pattern to the transmission line 5, sending out the non-priority data frame in the transmission/reception data buffer section 2 is started.

When the sending is completed, the F pattern is sent again and the state variable is set to "0".

(111) When the state variable is "O" and a request for priority frame transmission is generated through the interface line 4, the control section 1 requests the character calculation section 3 to generate the F pattern and sets the state variable to "1". shall be.

After sending the F pattern to the line 5, sending out the priority frames in the transmission/reception data buffer section 2 is started.

When the transmission is completed, the F pattern is quickly output again and the state variable is set to "0".

(IV) When the state variable is "1", even if a request to send another frame occurs, the control unit 1 will not accept this request until the sending of the previous frame is completed.

(V) If the state variable is "2", do the following.

(2) When a priority frame transmission request occurs through the interface line 4, the control section 1 saves the frame currently being transmitted, sets the state variable to "3", and requests the character calculation section 3 to generate the F pattern.

After sending the F pattern to line 5, it starts sending priority frames, but after the sending is finished, it sends the F pattern again, sets the state variable to "2," and resumes sending the non-priority frames that were saved earlier. .

Frame stealing in this case is shown in FIG. 1C.

In other words, if there is no priority frame transmission request, F
+1 t C1+ 111 y■1□, Fe12
, F should have been sent in the order of non-priority frames, but due to a request to send a priority frame, a priority frame is interrupted and sent as shown in FIG. 1C.

(2) Even if a request to send a non-priority frame occurs through the interface line 4, the control unit 1 will not accept the request until the transmission of the previous frame is completed.

(If the vt state variable is "3", the control unit 1 does not accept a request to send a frame, as in the case of GV).

(11) Frame abandonment is performed by transmitting an abandonment pattern.

Whether this abandonment pattern is defined as different from the F pattern or the same as the F pattern is determined by the system convention, and the processing method in this case is defined as the operation on the receiving side.

In addition, this will be specified by the state variable management system in this case, but for example, following the transmission of the abandonment pattern,
One method is to send the F pattern and set the state variable to "O".

(When terminating the transmission, the control unit 1 instructs to transmit a communication termination pattern in which 15 or more bits of "1" are consecutive.

(2) Receiving side (1) After the data link is set up, if information can be received, the control unit 1 sets the state variable to "0".

(ii) When the state variable is "O", the control unit 1 performs the following operation depending on the next received bit pattern.

■ When the F pattern is detected, leave the state variable at “O”.
So I don't do anything.

■ When the F pattern or abandonment pattern is detected, the state variables are set as follows.

[Yes] In a system that equates the F pattern with the abandoned pattern, when this pattern is detected, the state variable is set to "2".

■ In a system that distinguishes between F patterns and abandoned patterns, when an F pattern is detected, the state variable is set to "2", and when an abandoned pattern is detected, this pattern is ignored and the state variable remains at "0".

■ When a communication end pattern is detected, the transmitting station interprets the transmission as having ended.

■ In cases other than the above, the priority frame is received and the state variable is set to "1".

(ilj) When the state variable is "1", "O" is inserted into the received signal as priority frame data until the next specific pattern is detected, and the removal section 31 removes "O" inserted due to transparent transmission. The calculation check section 32 also checks Fe2.

The state variable remains "l" and does not change.

■ When an F pattern is detected, the received data up to that point is processed as a priority frame, and the state variable is set to
”.

■ When an F pattern or an abandonment pattern is detected, the frame currently being received is discarded.

Management of the state frequency is determined by the system, but for example, the next time the F pattern is detected, the state variable is set to "O" and the state returns to the initial state.

■ When a communication end pattern is detected, the transmitting station interprets the transmission as having ended.

■ If the state variable is 12'', 0'' inserted for transparent transmission is removed as non-priority frame data until the next specific pattern is detected, and F
Check e2.

The state variable remains at "3" and is not changed.

(2) When the F pattern is detected, it is interpreted as a priority frame interrupt, the received data so far is saved, and the status variable is set to "8".

■ The processing when an F pattern or an abandonment pattern is detected is as follows.

■ In a system that equates the F pattern with an abandonment pattern, when this pattern is detected, the control unit sets the state variable to "0" and processes the received frame, but first it determines whether this frame is a normal frame or an abandoned frame. Identification is required.

In other words, there is no error in Fe2 and the frame order is correct. The frame is considered normal only if it is correct.

In this case, checking the frame ordering have the same transmit sequence number, e.g. If frames with are received one after the other considers later frames as correct. Ru.

(2) In a system that distinguishes between F patterns and abandoned patterns, when an F pattern is detected, the received data up to that point is processed as a non-priority frame, and the state variable is set to "0".

When an abandonment pattern is detected, the data currently being received is discarded.

Management of state variables is specified by the system. For example, next we will take the F pattern. At the time of detection, the state variable is set to "0", Return to initial state.

■ When a communication end pattern is detected, the transmitting station interprets the transmission as having ended.

(V) When the state variable is "3", 0" of transparent transmission is removed as priority frame data and Fe2 is checked until the next specific pattern is detected.

The state variable remains at "3" and is not changed.

■ When the F pattern is detected, the received data up to that point is processed as a priority frame, and the state variable is set to "2".
” and starts receiving processing of non-priority frames again.

The subsequent operation is the same as (IV).

■ When an F pattern or an abandonment pattern is detected, the frame currently being received is discarded.

The processing in this case is determined by the system, but the following methods are available, for example.

■ A method of setting the state variable to "2" and starting the priority frame reception process again.

■ A method of discarding both the non-priority frame and the priority frame currently being received using one discard pattern, and then receiving the F pattern and returning to the initial state by setting the state variable to "0".

■ When a communication end pattern is detected, the transmitting station interprets the transmission as having ended.In this way, by defining the frame structure of priority frames and non-priority frames, and following the operation procedure described above, HDLC In a data frame transmission method using , it is possible to transmit one frame by interrupting the transmission of another frame.

As explained above, according to the transmission method of the present invention, it is possible to interrupt and transmit another frame during the transmission of a frame on the same line and logically the same transmission path. This method has the advantage that it is possible to transmit short data while transmitting long data, or to transmit data with high urgency or priority and various control signals while transmitting data with low urgency or priority.

For example, as an application example of the method of the present invention, when long data and short data are transferred together in a packet switching network, there are the following advantages.

(1) When transmitting long data such as fax image information through a packet-switched network, packets, which are short data, can be transferred by interrupting the data, so the packet transfer is not affected at all.

(2) Conversely, in order to be able to transfer long data as is,
For example, the trouble of disassembling and assembling packets of a certain length such as 128 bytes or 256 bytes can be omitted.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a frame structure of a priority frame and a non-priority frame, and an example of a transmission frame when a priority frame interrupts the transmission of a non-priority frame, and FIG. 2 is a diagram showing an example of a transmission frame used in the transmission method of the present invention. FIG. 2 is a block diagram showing an example of a transmission control function. F: Flag sequence (“01111110”), A,
A1, ni2 Near address field, C, C1゜C2
: Control field, I? 1111 I+2 t I2
”Information field, Fe2.Fe81.Fe82:
Frame check sequence, F: Flag sequence of non-priority frame, 1: Control unit, 2: Transmission/reception data buffer unit, 3: Character operation unit, 4: Interface line with other processing units, 5: Transmission line, 6: Transmission control Functional unit, 30: Specific pattern occurrence detection unit, 31: “O” insertion/removal unit, 32
:FC8 calculation check section.

Claims (1)

[Claims] 1. In a data frame transmission method that inserts codes indicating the start and end of a series of data and transmits them as a data frame, the codes at the start and end of a data frame to be prioritized and those of other non-priority data frames are A data frame transmission method characterized in that the start and end codes are different, so that a priority data frame can be transmitted by interrupting the transmission of a non-priority data frame.