JPS61125252A - Transition and interruption system of medium access control state - Google Patents

Abstract

PURPOSE:To improve the overall throughput and to minimize the load of an MPU by performing the normal state transition at each node by a TPC-dedicated hardware independently without the control by the MPU, interrupting to the MPU against the abnormal state to control. CONSTITUTION:A token passing controller (TPC)10 is included in an adapter of each node, and inputs transmission data 600 in the repeating status. The controller 10 also stores the processing result from the MPU20 in an RAM40 after transferring the data by DMA to a receiving buffer 50 without the controlling by the MPU20. The transferring data is transferred by DMA to the transmit/receiving buffer 50, and is made in transmission-ready status. If a token is transferred from other node, the TPC10 controls so that the repeating status transits to the token-holding status. And at the time when the transmitting of the transmit frame from the transmission buffer 50 is finished, the TPC10 controls so that the status transits to the token transmitting status. And it finally transmits the token, and further and again controls to transit to the repeating status by detecting the last byte of the frame. In the recovery status, the disappearing of the token is detected, the transition is informed by the interruption of node to the MPU, and its reason is indicated to the MPU.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an access method to a transmission medium of a local area network (LAN) that connects a plurality of 81 computers by communication within a geographically close area. 1. In particular, the present invention relates to a medium access control state transition interrupt system of the l.-kun system in which only a computer that has captured a free token in a ring-shaped transmission medium has the right to transmit.

In recent years, the era has shifted from centralized processing by a central processing unit (CPtJ) to separate processing by multiple workstations. Local area networks (LANs), which organically connect computers located in geographically close premises or buildings through communication networks to execute distributed processing and office automation at high efficiency, have been attracting attention.

By effectively utilizing this LAN, it is possible to efficiently transfer programs, text, or image data between work stages, input/output to a large-capacity shared file device, etc. Typical LAN coupling methods include a bus type and a ring type. Whether it is a bus type or a ring type, in a LAN, the unit of data transfer is mainly a packet consisting of data and sending/receiving addresses, etc., but in this case,
Because multiple workstations called nodes share the transmission medium.

Coordinating access to a medium, i.e., based on a communication protocol called a communication protocol.

It is important to make access selections. Therefore.

Basic properties of the network by access method.

In other words, characteristics such as transmission capacity (how many passwords can be transmitted per unit time), measures against failures, ease of system design, etc. are determined.

(Prior art) Conventionally, the access method for this type of LAN is C.
SMA/CD (Carrier 5ense
multiple access/collisio
detection) + time slot method and token passing
) method. The C3MAlCD method is Isane 7
In this method, a node that has a bucket number to send immediately sends it if the lotus is free.

This method suspends transmission when the bus is in use, waits an appropriate amount of time before retransmitting, and then transmits again. The time slot method is a method in which a fixed period of time is divided according to the number of nodes, and each node is allowed to transmit packets only in a predetermined time slot/period, or time slots are allocated according to requests. Finally, in the l-kun passing method, packets called fleet tokens representing transmission rights are mainly circulated through a ring-shaped transmission medium, and the node that wants to send waits until a token comes around and takes the token into it. In general, there are two types of methods for coupling LAN nodes to the transmission medium: bus type and ring type, but the bus type mainly uses the C3MA/CD method. However, the disadvantages of the bus type are that it is not suitable for long-distance networks or high-speed networks in principle, and that optical fibers are difficult to use5.In particular, as the load increases, 1fi The drawbacks are increased delay and reduced transmission efficiency. Therefore, the token ring method is said to be the most efficient when the load is large. That is, it has the advantage that even when the load is increased, the change in delay time does not increase rapidly, the transmission capacity is high, and the maximum delay time is determined by the propagation delay between the rings. However, the disadvantages are that a failure in one link-like disconnection affects the whole, packets continue to circulate, and tokens are lost, so a function to deal with this is required.

Conventional Art 3 Most of the media access control in this type of token ring system was performed using microblocks, ie, firmware, in each node. Therefore 1
The microprocessor cannot perform other work while the firmware is executing the control to transmit the frame data and re-send the token after capturing the token, thus reducing the throughput of the node. This has the drawback that not only does this reduce the data transmission capacity of the entire ring, but also the data transmission capacity of the entire ring decreases.

[Problem that the invention seeks to solve]

In order to eliminate the above-mentioned two drawbacks of the conventional technology, the present invention provides, in the token ring system, state control such as transmitting frame data and re-sending the token after capturing the l--kun, independently of the firmware. This solves the problem of how to separate the dedicated hardware and firmware so that it can be executed on dedicated hardware.

[Means for Solving the Problem] The present invention provides a local area network in which access rights to a ring-shaped transmission medium are controlled using tokens, in which each node maintains a plurality of states in order to perform medium access control (MAC). They are classified into normal states and recovery states, transitions between states classified as normal states are not notified to the node's processor, and transitions between states classified as recovery states are not notified to the node's processor. An object of the present invention is to provide a medium access control state transition interrupt method characterized by notification by.

[For production]

In the token ring system, the present invention provides a repeat state in which each node has not yet captured a token when it is normal, a token holding state in which it captures a token and transmits a frame, and a state in which it detects the end of a frame and transmits a token. The three states of the token sending state are defined as normal states so that they can be easily replaced by the dedicated heartware, and the transition of these states is executed by the dedicated hardware (1, 3I) without the control of the CPU. 1. Recovering operations from abnormal conditions such as "No connection" or disconnection are notified to the firmware via an interrupt.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 fat is 2 Medium access control (MAC) of the present invention
A circuit block diagram illustrating the transition interrupt method.

In a local network (LAN) in which multiple pointers called nodes are connected to a ring-shaped communication path, only the node that captures a free token (hereinafter simply referred to as a "token") has the right to transmit. Based on this principle, each node has dedicated hardware that controls transition states between normal states and an access control circuit that performs recovery from abnormal states according to a microprogram (firmware).

In the case of the token passing method, generally when a 3-byte token is passed around the ring and a certain node captures the 1.-kun, it has the right to transmit and sends a data frame. There are several methods for determining when to release the token when the node finishes transmitting, but in this example, the node releases the token after it finishes transmitting the data frame and when it recognizes the header of the frame. The method is to transfer transmission rights to the peer node by flowing tokens. The above token passing method will be explained with reference to FIG. For example, Figure 3 fal is
Four nodes A, B, and C in a ring.

If D is connected, there is a fleet token between C and D, with no node in F, A, B, C, or D capturing the token.

This is a repeat state in which frames can be received and the same data can be streamed. In the same figure fbl, node D is fleet-
In the state in which the node D has captured the token, the node D enters a state of holding a token, that is, a state of waiting for the right to transmit a Freno.

At this time, the other nodes A, B, and C remain in the repeat state. At tel in the figure, node D is in a state where it sends out a busy token to the ring while continuing to hold the token. Therefore, when node D is in the token holding state, it can send a busy token, but the other nodes A and BC, which are in the repeat state, repeat fleet tokens and busy tokens.

In the same figure (d+, node D finishes transmitting the frame and enters the token sending state. In the figure te+, the node D enters the token sending state.

Node D continues to be in the token sending state, but note 'B, which is in the 5-repeat state, is receiving frames. In the same figure (fl), if Note "D recognizes the frame header while continuing the token sending state, it is in a state where it sends a free token and removes the busy token. Then, as shown in the same figure fgl, , node D has finished removing busy tokens and is in the repeat state again.

Therefore, frames are not repeated in the token holding state and the token sending state. In such a token passing system, the problem is how each node actually controls access.

In order to solve this problem, the present invention is characterized by first classifying the states and further classifying the states into a normal state and a recovery state.

Figure 2 shows a state transition diagram. In order to distinguish between a case where a token is captured and a case where a token is not captured, we first define a repeat state φ or a state where a token is not captured. In this state, it only has the function of receiving frame data from transmitting nodes within the ring. Additionally, in this state, it has a so-called repeat function that allows the same data to be streamed at the same time it is received. In this state, if a token is captured, the token will become held state ■ or ■.

The token is released when the frame data has been transmitted, but the period until that state is reached is called the token sending state ■ or ■. After the token sending is finished, the token is repeated again. The state will be either ■ or ■.In this way, if the ring node is normal, the removed node will repeat this state of ■, ■, ■ or ■, ■, ■.This ■, ■, ■, or ■ ,
■.

Define the state of ■ as a normal state.

Each node also has the function of removing its own frame when it is not in a repeat state. Namely.

When you are in the token holding state ■ or ■ and send out frame data, when that frame data returns to you, remove that frame data to prevent that data from going around the ring many times, It also includes a function to confirm that frame absorption has been completed.

Furthermore, each node has a function of reproducing tokens when they run out, but instead of randomly reproducing tokens, only a specific node, that is, a node called an active monitor (AM), can reproduce tokens. At this time, a node that is not an active monitor, that is, a normal node that does not perform token regeneration, is a passive monitor (P
It is called M). In this method, a sequence that becomes AM or a sequence that plays 1-kun,
Alternatively, the sequence for issuing an abnormality notification frame when a ring is disconnected is a state transition.

The state for reproducing a token is called the token regeneration state ■, the state for transmitting a frame to reach 8M in PM is called the monitor recovery state ■, and the state for reproducing an error notification frame is called a beacon state This is called the sending state ■. This ■.

The state of ■5■ is defined as the recovery state.

In AM or PM, there are timers that monitor the status, including timers 11-15.

Timer 11 is called the T+ timer, and the AM monitors the time that frames do not flow from the ring. Measure time T1 (several tens of ms). this is.

This is a timer for token regeneration. T2 timer 12
is a timer that is activated in both PM and AM, but monitors the relatively long time when only tokens do not flow. For example, in the case of an abnormal state such as a disconnection or no rAM, the token will not flow. The time of T2 is usually 1 to 2 seconds. When the T2 timeout occurs, the P
M is in the monitor recovery state ■. The T3 timer 13 is a timer that limits the time for holding 1.-kun in the token holding state ■. The T4 timer 14 operates in the token sending state (2) and controls the timing of issuing tokens. In other words, the time is monitored so that no token is issued until the frame is sent out and the header is recognized. That is, when a frame is broken, a T4 timeout occurs, so it is determined that the frame is broken and a token is intentionally issued. The T5 timer 15 is a timer that measures the timing at which a monitor recovery frame is issued several times when the monitor recovery 13 is in state ■.

Next, a sequence for generating an AM state using these timers 11 to 15 will be described. First, when the power is turned on, the node is in the PM repeat state.

If a token does not come in this state, the l-kun holding state (■) cannot be reached, so the T2 timer 12 measures the time. When the T2 timeout (1 to 2 seconds) occurs, the node enters the monitor recovery state ■. A node in the monitor recovery state (■) sends out a frame for recovery called a monitor recovery frame. There are source and destination address fields in the frame, and since the source address is its own address, this prevents conflicts between nodes in the ring that are in recovery at the same time. In other words, a request to a node that wants to become an AM is to send a monitor recovery frame, but when it is in the monitor recovery state φ and receives a monitor recovery frame from another, the source address (SA) in the frame and Compare with My Address (MA). If SA>MA, the node abandons the monitor recovery state (■) and enters the repeat state (2). The frame is then routed downstream. If you repeat this, only one node with the maximum address among the nodes that have reached T2 timeout will be in the repeat state.■
Maintain the monitor recovery state ■ instead. and T1
1 (several l1ls) Continue the monitoring state (■). In other words, the monitor recovery frame is sent out, and SA=M in the last remaining monitor recovery state ■ note.
Only when it receives A's monitor recovery frame does it recognize that it can enter the AM state. Then, the state becomes the AM state repeat state (3) and becomes the normal reception state, and this becomes the only AM state in the ring. When a node cannot capture a token in the repeat state ■ of the AM state and T1 timeout (several tens of ms) occurs, the AM node enters the token regeneration state ■ and sends a ring barge frame (RP
F). This is a state in which frames can be streamed even though there is no token. When this RPF is sent, the AM node enters the token sending state (■). That is, the ring is again in the "token present" state, and this AM node continues in the three normal states ■, ■, ■.

PM also continues in the states of ■, ■, and ■.

Note that if there is a disconnection somewhere in the ring, a certain node will transition from the repeat state to the monitor recovery state.At this time, since there is a disconnection, the node will not be able to receive the monitor recovery frame for its own address MA. When it becomes impossible and the state transitions to the point where retryout is detected, and this process is repeated about 100 times without success, the beacon sending state (■) is entered. This is because the node immediately below the place where the communication path in the ring is broken is in this state, and there is a possibility that there is a break between this node and the node above it, and it is also possible to detect a break. Become.

Next, a description will be given of dedicated hardware that performs normal control using the above three states, ie, the repeat state, the token holding state, and the token sending state, without involving the control of the processor.

A token passing controller (TPO) 10 is included in each node's adapter, as shown in FIG. 30 ROM for program storage, 40 RAM for work storage
and its common bus 6 along with transmit/receive buffers 50
0 and inputs the received data 600 transferred bit serially from other nodes on the ring communication path in a repeating state while maintaining synchronization, and the received frame data is transferred to the receive buffer 50 without the control of the microprocessor 20. After DMA transfer to.

It is processed by the microprocessor 20 and the result is stored in the RAM 40. Data to be transferred to another node is transferred to the transmit/receive buffer 50 by DMA via the common data bus 60 and becomes ready for transmission.

When a token is transferred from another node, the TPO controls the transition from the repeat state to the token holding state, and returns to the token sending state when the sending data frame from the sending buffer 50 has been sent. Control the transition. Finally, by sending out a token and detecting the last byte of the frame, control is executed to shift to the repeat state again. This TPC
Due to the existence of , such state transition for access control can be performed without being controlled by the microprocessor 20 . As shown in FIG.
The data is transferred to the receiving circuit 102 under the control of 03, and then transferred to the receiving buffer 50 under synchronous control. And after token capture.

From the token holding state to the token sending state, the frame data transferred from the transmission buffer 50 is transferred to the transmission circuit under the control of the control circuit 103, and under synchronous control, the repeat circuit 101 converts the bytes from parallel to serial and converts the frame and token. It is output from the output 601 in bit serial form.

Next, the TPC repeat circuit 101 and its peripheral circuits will be explained using FIG. 6.

600 data RXD transferred in bit serial
First, convert it into a byte using the serial/parallel conversion circuit R3R1012.

At this time, first, to check whether it is a frame, a specific FS pattern is sent to the data line 600, and the first pattern of the frame is compared with the same FS pattern. . A frame is a 9-bit byte, for example, starting with 9 bits of the FS pattern, MAC3fl+ and MACCS f21
are each 9 pin] bytes, then the destination address and source address are 6 bytes each.

The fields are configured such that the command and data are n high, the check code is 4 bytes, the file encoder (FE) code 1- is 1 byte, and finally the status is 1 high. First, in order to become a hide, it is serial-parallel converted by R3R, and the bit pattern is compared with the FS pattern, and if they match, it is confirmed that it is the beginning of the frame, so it is possible to pretend that Freno reception has started.
Pflo.

The input FF 1014, that is, the RXFRM signal is sensed. Since the next 1 hide of the FS pattern is 9 bits later, the 4-bit counter 10 is reset at the beginning of the frame.
15 counts from 0 to 8, and when RCN=8, the repeat circuit knows that R3R is setting the next hide. This sequence is then repeated within the frame. On the other hand, the BFA buffer 1017 temporarily holds each byte. This temporarily held byte data is transferred to the receiving circuit and is counted by the receiving sequence counter (R3CN) and receiving address counter (RA).
CN) to identify each field within the frame.

Then, the former counts the number of ``high'' in field 1', thereby knowing whether the byte is like . Namely.

If the byte is an address part, a comparison can be performed with a previously prepared address, for example, SA and MA can be compared.

Also, if it is a command part, use it.

Connection can be made so that the sequence moves to compare the addresses of SA and MA in the monitoring state (2).

r (The two registers BFE and BFO connected to the FA buffer 1017 are buffers for synchronization. In other words, the self-synchronized clock obtained by bit synchronizing the received data is different from the clock to be transmitted. To cover this, there are BFO and BFE, each of which is
The data is shifted and sent in accordance with the advance and lag of the clock phase, and odd and even bytes are sent alternately. The frame input in this way is input to the BFE and BFO, and the control circuit decides whether or not to take it out from there, and the transmission register TSR102
Put it in 0. TSR1020 is a parallel-in/serial-out shift register.

The TFG flip-flop connected to this TSR 1020 is a generator that alternately generates 1 and 0.

(If there is no frame, the TSR is 1010...
・I am trying to send the following pattern.

Next, correspond to each state in the state transition diagram of FIG.

The state flip-flop for state expression existing in the status control section of the 2l-TPO will be explained using FIG.

For the TPO state flip-flop (F/F).

Active monitor (AM), repeat (RIEP)
.

Token holding (TKNHD), )-Kun sending (TKNP
S), ) - FO and Fl respectively express the states of playback (TKNGR), monitor recovery (MREC), and beacon transmission (BCPS).

F2. F3. F4. F5. There is F6. First, when the power is turned on, repeat 1-F/F of Fl is set to 1''.

Alternatively, Fl is set to 1'' during initial setting by Far J and Ware.

At this time, this node enters the repeat state of the passing monitor state. When a token is input to the TPC repeat circuit 101, it is composed of three bytes: FS, MAC3, and FB. This token is in turn launched into the BFA buffer 1017, and when TCP recognizes token capture, Fl
Reset the repeat F/F and hold the F2 token F
/F is cented to l゛. At this time, the token is in the state of being absorbed by this note, and the l・-kun is not repeated, but is in the kill state, and the lower node l
− will not be forwarded to. The token holding F/F is “
1”, the TSR 10 in the repeat circuit 101 transmits the transmission frame prepared in the transmission buffer 50.
20 and send. At the end of the transmission, it enters the token sending state, resets the token holding F/F of F2, and sets the 1-kun sending F/F of F3 to "1". If you send a token after sending a frame, it will go into a repeat state again.

At the same time as resetting the token sending F/F, the F/F is reset again.
Set the repeat F/F to "l".

When the repeat F/F of Fl is set to "1" and the node is in the repeat state, when a timeout occurs in the T2 timer, the monitor recovery F/F of FS representing the monitor recovery state is set to "1". . And monitor recovery frame TSL'? 1020 to the ring.

It checks whether the frame has been returned after circulating around the ring and compares the source address (SA) in the frame with its own address (MA>.As mentioned above, if SA>M
At the time of A, the monitor recovery F/F of the FS is reset in order to return to the repeat state. And SA=M
If A, this node becomes the active monitor.

At the same time as resetting the F5 monitor backup F/F, set the FO active monitor F/F to 1'', and also set the FL repeat F/I? to 1''. In other words, this node is in a repeat state of active monitor state. And ]・-kun hold, token sending 2
And if you can repeat the repeat, F2. F3
Repeats the three states while being beaten seven times. However, in the repeat state, when the T+timer reaches T+timeoutl, the token reproduction F/F of F4 is set to "I". When the token is regenerated and transferred to the ring, F4 is reset, the token sending F/F representing the 1-kun sending state is set to "1", and the token is played back. Note that when comparing SA and MA in the passive monitor state, if SA≠MA always within T5 time, this node cannot become an active monitor and enters the beacon sending state, so the beacon sending F/F of F6 is 1". Also, this F6 is in a repeat state when receiving BCF, so it is reset, but when a disconnection is detected, it is sent again.

Next, the MAC transition interrupt system of the present invention will be explained using FIG. 1 (δ).

In the present invention, each node performs MAC control.

In the state transition diagram shown in Figure 2, it is classified into normal states of ■5■, ′■ (or ■, ■, ■) and recovery states of ■, ■, ■. The TPO executes the transition between repeat states without notifying the processor 20 of the processor 20, and notifies the processor 20 of the transition between the repeat states by an "interrupt" and presents the reason for the 1 transition to the firmware of the processor 20 using an interrupt cause display register. It is characterized by In other words, the normal state of the format and timing of sending and playing frames and tokens at Masatomi is controlled by the TPC.
In this LSI, the firmware automatically and independently performs the recovery without being aware of it, and the recovery for "1-kun missing" or "AM missing" etc. is controlled by notifying the firmware by interrupt, thereby reducing the loss of 2 hours. will be removed.

If all state transitions are executed by firmware, there will be a considerable delay in the normal state transition from capturing the 1-kun to sending out the frame and sending out the token, and the microprogram will execute during this time. Other work to be done is completely waiting. The control of accidental recovery is notified to the firmware and all execution is performed by the firmware to improve efficiency. In other words, “
In case of an accidental state such as "no token", "no AM" or "disconnection", the firmware itself prepares a frame for recovery, the firmware consciously transmits the frame, and the resulting frame is also notified to the frameware. For example, in monitor recovery state ■, when a monitor recovery frame is sent, the comparison between SA and MA is executed in the heart of the TPC, that is, the LSI, but the signal to "become AM" is notified to the firmware by an interrupt. . When the firmware recognizes that it has reached 8M, the firmware itself detects the state. in this way.

There are the following interrupts to the fur 12ware in the recovery state.

'FI timer interrupt; The TI timer operates in the active monitor repeat state (2), and times out in several to several tens of seconds if neither the token nor the frame J passes. This is notified to the firmware via an interrupt. The firmware sets the state to token regeneration state (■) and sends out an RPF (Ring Barge Frame).

The TI timer is restarted when a token or frame passes.

T2 timer interrupt: The T2 timer operates in states other than monitor recovery state ■ or beacon sending state ■, and times out in a few seconds if no token passes. This is notified to the firmware via an interrupt. The firmware sets the state to monitor recovery state.

Send MRF. Restarts when the token passes.

T5 timer interrupt: T3 timer operates in monitor recovery state ■,
It times out after several 5 seconds.

This is notified to the firmware via an interrupt.

The firmware changes the state and sends out a monitor frame.

AM acquisition interrupt: In the monitor recovery state (■), when a monitor recovery frame with SA=MA is received, an interrupt is notified, and the firmware changes the state to the active monitor repeat state (■).

MRC release interrupt: In monitor recovery state (■), when a monitor recovery frame with SA>MA is received, an interrupt is notified. Set the firmware to passive monitor repeat state■.

BCPS release interrupt: In the beacon sending state (■), when BCF is received, an interrupt is notified, and the firmware enters the passive monitor repeat state (■).

When the RPF of SA#MA is received in the AM release interrupt near active monitor state, the firmware that notifies by interrupt enters the passive monitor repeat state.

Therefore, in the state flip-flops FO to F6 of FIG. 7, the signals marked * are sent to the firmware.

Next, fat in FIG. 1 is a part of the TPC receiving circuit that generates interrupts, and is the above-mentioned timer T + .

T2. A comparison of SA and MA is also performed, including T5.

When the first FS pattern of the received frame is confirmed.

The hide data is transferred to the receiving circuit, and the 5 receiving sequence counter (R3CN) 1020 and the receiving address counter (CN to R)] 021H! This allows you to identify each field within the frame. For example, BFA buffer 1017
If the input byte is the address part SA, the counters 1020 and 1021 are sent to the decode circuit 1022, and the comparison circuit compares the decode signal with the own address (MA) prepared in advance selected from the node address register 1023. It can be executed with 1024. When SA=MA, 1 is sent to the flip-flop that was set to 0 during initialization.

Then, when a specific bit of the control register from the pro sensor 20 becomes valid, that is, the output of the AND circuit 1027 becomes "1", and the reception status 102
A bit indicating SA=MA is sent in 8, and is provided to the control circuit section 103.

The contents of the reception status register RXF3 are shown in Figure 1 (bl
As shown in the figure, the 1st bit and θ bit are 00 for the non-coverage frame, and 01 for the ring purge frame (RPF).
, 10 is the monitor recovery frame (MRF) and 1
1 indicates a beacon frame (BCF), 00 indicates SA=MA, and 01 indicates SA>M in the 3rd and 2nd bits.
A, 10 represents SA<MA, and 11 represents frame abort. FC3E of 4th Pitsu I is FC on own node
When an S error is detected, seven steps are performed.

Error detection is shown in Figure 1 (RCRC of the receiving circuit 102 of al.
BFA buffer 1 with register and CRC calculation circuit 1030
The comparison circuit 1031 compares the result of the CRC operation on the check code marked 017 with a constant 1032. If there is a mismatch, the firmware is notified of the abnormality. Also.

At the end of the frame, the comparison circuit 1033 compares the received FE pattern with a predetermined FB pattern, and if they do not match, an interrupt is issued to the firmware.

In this way, the present invention provides a local area network in which access rights to a ring-shaped transmission medium are controlled using tokens, in which each node performs medium access control (M
AC), it has multiple states, which are classified into normal state and recovery state. Under normal conditions, fleet tokens are captured, and after the frame is sent, fleet tokens are captured.
In the recovery state, it detects the disappearance of fleet tokens and regenerates them, or controls to acquire the right to reproduce fleet tokens. or.

Controls the transmission of frames to notify abnormalities. At this time, transitions between states classified as normal states are not notified to the node processor, and transitions between states classified as recovery states are notified to the node processor by an interrupt, and the reason for the transition is displayed as the cause of the transition. It is characterized in that it is presented to the processor by a register.

〔Effect of the invention〕

In this way, in each node, the transition between the normal states of the repeat state, token holding state, and token sending state is independent of the processor without going through the firmware of the microprocessor (MPU). The TPC-dedicated hardware executes the process, and in response to abnormal conditions such as ``no token'', no AM'' or disconnection, the firmware is controlled by interrupts.

M PtJ not only improves the overall throughput by performing other tasks while the TPC is executing state transitions and checking the transmission medium in abnormal states, but also improves the firmware for the MPU. This has the effect of reducing the burden and therefore making system setup extremely easy.

[Brief explanation of drawings]

FIG. 1al is a block diagram of a part of a TPC receiving circuit that generates an interrupt according to an embodiment of the present invention. FIG. 1B is a diagram showing the contents of the reception status register RXT3 in FIG. 1A. FIG. 2 is a state transition diagram of the medium access control state transition interrupt method of the present invention. Fig. 1 al~ (gl is an explanatory diagram of the token passing method. Fig. 4 is a configuration diagram of the adapter in the token passing method. =33- Fig. 5 shows the program of the token passing controller provided in the adapter shown in Fig. 4.・Tsuku diagram. Figure 6 is a repeat circuit diagram of TPC. Figure 7 is a diagram showing the status control section of TPC. 102... Reception circuit. 1026... Control register. 1028... Reception status register -34=ヱCDI, ′:L also ゝ■ -See yo℃

Claims (2)

[Claims] (1) In a local area network where access rights to a ring-shaped transmission medium are controlled using tokens, each node has multiple states to perform medium access control (MAC), and these are a normal state and a recovery state. A medium access system characterized in that a transition between states classified as a normal state is not notified to a node processor, and a transition between states classified as a recovery state is notified to a node processor by an interrupt. Control state transition interrupt method. (2) In the normal state, the free token is captured, and after sending the frame, the free token is sent out, and the control is performed to receive the frame addressed to the own node. In the recovery state, the loss of the free token is detected and regenerated. The medium access control state transition according to claim 1, characterized in that the medium access control state transition is performed to acquire the right to perform or reproduce a token, or to transmit a frame for notifying an abnormality. Interrupt method.