Structure of input and output data:
The module is a combined special function input and output module with 1 x 32 (40) Bit input and output data. The tranfer of the data to be transmitted and the received data is made via up to 5 input and 5 output Bytes. One control byte and one status byte are used to control the floating data.
The control byte consists of the following bits:
Control byte
Bit 7
0
Constant value always must be 0
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
The status byte consists of the following bits:
Status byte
Bit 7
0
Constant value always must be 0.
Bit 6
Bit 5 | Bit 4 | Bit 3 |
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| RCVT1 | RCVT2 |
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| Module is in timeout. | The receiver is in |
| All output bits are set | timeout. |
| to 0 (watchdog). |
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Bit 2
CHK
Checksum error.
Bit 1
OVR
Buffer overflow
Bit 0
PAR
Pariry error or wrong data in a frame.
The PLC is able to control transmission and reception of data by means of the control byte and the status byte.
Control of the multiplex connection: In the process image of the transmitting buscoupler one Bit is set to „1“ for the whole time. As long as this Bit is „1“ in the receiving coupler, further input Bits can be evaluated. If the Bit is „0“ the multiplex connection has been disrupted. The further Bits are also 0 because of the watchdog.
Control of the multiplex connection with acknowledge: If the transmitting buscoupler gets an acknowledge from the receiving buscoupler, the received bit must be transfered as an output bit to the process image. The transmission is successful as long as the Bit is „1“.
Handshake: If a serial data exchange should be made with the data exchange module, the handshake can be made via „Toggle Bits“. Therefore an input bit and an output bit are reserved. As soon as those bits are different from each other, a request from the opposite module is made. As soon as the request is executed the output bit is toggled.
Dataexchange module | 4 |
