JPH02238744A - Communication system - Google Patents

Abstract

PURPOSE:To attain efficient operation without using any special hardware by using a parity bit as a reception station designation bit and sending a signal while the polarity of the parity bit is inverted when a reception station is designated. CONSTITUTION:Addresses of stations B-D are constituted and when an odd number parity bit is normally added to the address respectively, the signal is sent while the polarity of the parity bit added in the reception station address designated by a reception station is inverted. Figure shows the case when a station B is designated, and in this case, the parity bits are inversed as shown in figure to be level 1. Since the parity bit is used as the reception station designation bit and the polarity of the parity bit is inverted through the designation of the reception station for the transmission of the signal in such a manner, the efficient operation is attained even without using a special hardware.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to facsimile machines, copying machines, etc.
The present invention relates to a communication method that is suitable for use when performing predetermined control by communicating between a plurality of stations having an MPU configuration, and particularly to a communication method that can be operated efficiently without using special hardware.

[Background of the Invention] In recent years, electronic devices have become capable of complex control and are equipped with many functions, so that multiple MPUs are increasingly used. In this way, multi-MPU
When configuring a device control system, etc., each MPU
It is necessary to connect stations (hereinafter simply referred to as stations) with each other to enable communication between designated stations.

As a communication device with such a multi-MPU configuration, the fifth
The configuration shown in the figure below is known.

FIG. 5 shows an example of a half-duplex communication device 10, in which an MPU
A plurality of stations 12, 14, 16, .
24, 26, . . . are connected to a common transmission path 48.

In this communication device 10, management between stations is performed by software. For example, when station 12 is a transmitting station, other station 1
4.16. . . . always manages the process of determining whether it is a receiving station or not, and the tracking of state transitions as communication progresses, using software, regardless of whether it is a receiving station or not.

Figure 6 shows a dedicated hardware 32 instead of USART.
, 34.36. ..., the dedicated hardware 32, 34, 36 . The stations communicate with each other via...

Therefore, dedicated hardware 32.34.36.・・・
・is hardware for protocol monitoring.

On the other hand, FIG. 7 shows an example in which individual transmission lines are used to connect stations, and the transmission format in this case can be full duplex. In this example, station 12 is the master station, and USART 22 and other USART 24.2
A transmission path changeover switch 40.42 for the dedicated transmission path 44.46 is provided between the transmission path 6, .

A slave station is selected by selecting switch 40, 42.

[Problem to be Solved by the Invention] In such a communication device, monitoring between stations can be done either by software as described above or by hardware. With the exception of the example in the figure, during communication, including data transmission, not only the software (communication protocols) of the communicating stations are managed, but also the communication protocols of other stations. There is a need.

Therefore, in the configuration shown in FIG. 5 in which this communication protocol is managed by software, there is a problem in that the load on the MPU increases.

In order to process this using hardware, dedicated hardware for monitoring the communication protocol is required as shown in FIG. 6, which increases costs. In addition, when connecting with a dedicated transmission line as shown in Figure 7, the hardware is relatively simple, but the number of connected stations is limited, the mask station is physically fixed, and the communication between slaves is relatively simple. There are problems such as not being able to communicate directly.

Therefore, the present invention proposes a communication method that is particularly applicable to communication devices as shown in FIG. 5, and that allows efficient and flexible operation without using special hardware. .

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention has the following features:
In a communication system in which multiple stations with an MPU configuration are connected to a single transmission path, and communication between the multiple stations is performed via that transmission path, a parity pit is used as a receiving station designation bit. The present invention is characterized in that the polarity of the parity bit is inverted and transmitted when specifying a receiving station.

[Function] For example, in the case of communication between A station and B station, when data is transferred from A station to B station, this is inserted into the frame header of the transmitted data that can be sent from A station. Parity pit, e.g. receiving station address (i.e. station B)
The polarity of the parity bit that can be added to the signal is inverted and transmitted.

In this case, in stations other than station A, a parity error occurs when receiving the receiving station address, and an interrupt (INT) occurs due to the parity error, and the MPU of each station performs a comparison check with its own station address. When the received receiving station address matches the own station address (B station), the B station transitions to the receiving state.

Then, the next transmission data (for example,
1 byte) is taken into the MPU 14 and the received frame processing is executed.

On the other hand, when the receiving station address does not match the own station address, such as in station C, all data that is subsequently transmitted is discarded.

When the address of the own station does not match, the data is simply read and discarded, so the software configuration of the MPU is very simple and the load on the MPU is also very small.

[Embodiment] Next, a case in which an example of the communication method according to the present invention is applied to the above-mentioned communication device will be described in detail with reference to FIG. 1 and subsequent figures.

Half-duplex communication device 1 to which the communication method according to the present invention can be applied
Since the hardware configuration of No. 0 is the same as the configuration of FIG. 5 shown in the conventional example, the explanation thereof will be omitted.

Figure 3 shows an example of the configuration of a transmission frame. In this example, in addition to the reception station address, one frame is made up of the transmission station address, the number of bytes of transferred data, data, and CRC. .

A parity bit for parity check is added to each byte of this transmission frame. In this example, the receiving station is specified using a parity bit inserted into the receiving station address.

For example, as shown in FIG. When the station address of the D station is configured and odd parity pits are normally added to each, the polarity of the parity bit added to the receiving station address designated by the receiving station is transmitted with the polarity reversed. Ru. FIG. 4 shows the case where B station is designated, and in that case, the parity bit is inverted and becomes "1" as shown in the figure.

Now, let's look at an example of communication control when the polarity of the parity bit added to the receiving station address is inverted in this way.
As shown in FIG.

This example is applied to a communication device with a half-duplex transmission path, and the initial transmitting station is referred to as station A. Fifth
In the full-duplex configuration shown in the figure, station A becomes the initial transmitting station, first selects the opposite station (corresponding to the receiving station in the case of half-duplex), and then performs both transmission and reception between the two stations. operation becomes possible.

FIG. 1 is an example of initialization at power-on.

In the figure, among the terms described in each processing step,
Transmitter, Transmitting
, Receiving is a software flag indicating the transmitting station status/e% transmitting 71τ1 [A, receiving/llrA, respectively.

These flags are typically stored in memory and are used later to control the flow of the software.

Then, in step 51, the initial transmitting station is determined, and if it is the initial transmitting station, a transmitting station status flag is set by software. In this example, station A becomes the initial transmitting station.

At the same time, the flags indicating the transmitting state and the receiving state are both cleared.

Thereafter, USART 22 can be initialized for transmission (step 53). That is, through this step 53, initial settings for interrupts, input of received data, etc. are inhibited, etc. are performed.

On the other hand, in a station that is not the initial transmitting station, the transmitting station status flag is cleared and both the transmitting status and receiving status flags are cleared (step 54). and,
The corresponding USART is initialized for reception (step 55).

In step 52, when an internal transmission request occurs, the initial transmitting station whose transmitting station status flag is set sets the transmitting status flag, sets the USART to even parity mode, and then sends the receiving station address. USART
As shown in FIG. 4, a receiving station address with the parity bit of the specific receiving station address inverted is sent.

In this way, if the initial transmitting station is not set when the power is turned on, it will enter the transmitting station state, and during transmitting and receiving operations, the US
Processing is performed by interlabt generated by ART.

FIG. 2 shows an example of this interlove processing routine 6o, in which each station first checks whether it is in the transmitting state (step 61). For example, in the first communication, station A's If the transmitting station is B
The subsequent processing contents differ depending on the case where the station is a receiving station and the case where the station is a receiving station as described below.

To explain the processing on the side that is the transmitting station, in this case, first confirm whether the USART 22 related to the A station 12 is in a normal state, and then switch to odd parity mode immediately after sending the receiving station address. Reset (Step 6)
2) The data in the transmission frame is sent to MPU1 one byte at a time.
2 to the USART 22 (step 63).

In this case, the originating station address data is not sent in the first USART Interrupt after the start of transmission. USA
This 1-byte data is transmitted from the RT 22 to all stations other than the A station via the transmission line 48.

When the receiving station has been identified and all data for one frame has not been sent to the receiving station, the transmitting status flag of the transmitting station becomes the inhibit mode (steps 64, 65).

On the other hand, when the transmitting station is set to a non-transmitting station state, the following processing is performed.

In this case, it is possible to check whether the station is not a transmitting station, that is, it is a receiving station and is receiving data (step 61).
．． 71). In its initial state, it is not in the receiving state, so
When the USART status is confirmed, the MPU on the station side
One byte of data is received from the ART and a parity error check is performed (steps 72-74).

Since the polarity of the parity pit of the receiving station address is inverted, a parity error occurs regardless of whether the local station is designated or not (step 74). However, in the next step 75, the address is referred to as the own address.

When the receiving station address and the local station address match, the local station is assumed to be unspecified and set to receive mode.
Preparations for processing the received frame are completed (steps 75-7)
7).

If there is a mismatch, the interlab processing routine 60 is exited, and the received data is sequentially read and discarded.

Once the designated receiving station is set to the receiving mode, the following process occurs. In other words, in reception mode, if the USART of the receiving station is normal, the MPU
Now, receive 1 byte of data from USART and write 1
The received frame is processed in units of bytes (step 82), and when all the data in the transmitted frame has been processed, the receive mode is canceled and the process returns to the non-receiving state (steps 83 and 84).

Note that in order to transfer the transmission right to another station, the transmission right is notified to the specific station by executing the series of procedures for transmission described above. Data indicating the content of this notification is inserted into "data" in FIG. 3.

The station that has received the transmission right notification analyzes the data after completing the reception, and when it analyzes that it has acquired the transmission right, it can set its own station to the transmitting station mode. This specific station will now function as a transmitting station.

Note that in the above, a parity bit for specifying a receiving station is inserted in the receiving station address, but if the parity bit is inserted in a different position in the transmission frame, even if the parity bit is used, it will cause a burden on stations that are not related to transmission and reception. It is possible to make it smaller with a similar configuration.

[Effects of the Invention] As described above, according to the present invention, the polarity of a specific parity pit inserted into a transmission frame can be reversed.

In this way, the designation of the receiving station can be confirmed by reversing the polarity of the parity bit and matching the local station address, so a communication system using a common transmission path can be realized without the need for special hardware.

Furthermore, although a parity error occurs in a receiving station other than the designated receiving station, the subsequent processing is simply a process of reading and discarding the received data due to a reference mismatch in the own address.

That is, by reversing the polarity of the parity bit, it is possible to easily determine the cutoff of the transmitted frame, so that frame processing at stations other than the transmitting/receiving station can be almost eliminated. As a result, the software processing of the MPU is significantly simplified, and the burden on the MPUs of stations not involved in transmission and reception can be significantly reduced.

Incidentally, in conventional software processing, it was necessary to allocate about 20% of the software, although it depends on the frame configuration method, but with the present method, this becomes less than a few percent.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing an initialization processing routine when the communication method according to the present invention is applied, Fig. 2 is a flowchart showing an example of a USART interlab processing routine, and Fig. 3 is a flowchart showing an example of the interlab processing routine used in this communication method. FIG. 4 is a diagram showing the relationship between a receiving station address and a parity bit, and FIGS. 5 to 7 are diagrams showing a communication device with a multi-MPU configuration for explaining the present invention. This is a system diagram of 1 2. 22, 1 4. 24. 10... Communication device 16... MPU (station) 26... USART 48... Transmission line

Claims (1)

[Claims] (1) In a communication system in which multiple MPU-configured stations are connected to one transmission path, and communications are performed between the multiple stations via the transmission path, the receiving station designation bit is used as a receiving station designation bit. A communication system characterized in that a parity bit is used, and when a receiving station is specified, the polarity of the parity bit is inverted before transmission.