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7-4
RS232C Interfaces
7
7.3 Communication Specifications
[Communication parameters]
Communication method Start-stop system, text communication
Communication speed 9600 bps
Stop bit 1 bit
Data length 8 bits
Parity None
Terminate CR (both transmission and reception)
Flow control None
[Single channel and multi-channel]
Single channel Multi-channel
Topology Cross Ring
ID Unnecessary Host device 0
Drivers 1 to 9
Destination specification Unnecessary Add the destination ID at the beginning of the packets
From the host device to drivers: n****CR (n: slave station ID)
From drivers to the host device: 0n****CR (n: slave station ID)
[Transmission from the host device to drivers]
The number of characters to be transmitted should be 128 letters or less, including the slave station ID,
recognition key, transmission character string, and CR.
Recognition
key
Transmission character string CR
Single channel
Multi-channel
Recognition
key
Transmission character string CR
Slave
station ID
[Response from drivers to the host device]
The number of response characters should be 128 letters or less, including 0, slave station ID, recognition key,
transmission character string, and CR.
Recognition
key
Response character string CR
Single channel
Multi-channel
Recognition
key
Response character string CR
Slave
station ID
0
[Recognition key]
The recognition key is a function provided so that the host device can recognize that a response is a reply to a
specific transmission by the host device. A maximum of 15 “!” characters can be included in the recognition key
part. If more than 15 are added, the remainder of the number divided by 16 is processed as the actual recognition
key number.
When the host device transmits a message to a driver and attaches N recognition keys to the transmission
character string, the driver will send a response message back in which it attaches N recognition keys to that
transmission character string. If, for instance, the host device issues a transmission character string to a driver
that does not generate an immediate response, the host device may issue the next transmission character string
before the response is returned. In such cases, it becomes difficult for the host device to recognize to which
transmission character string the response character string returned afterward is issued. In this case, by issuing
transmission character strings with different recognition key numbers, it becomes possible to judge to which
transmission character string a particular response corresponds, simply by obtaining the recognition key number
as the response is received.