3-1-5. Communication Protocol
When the recorder receives a command from the control system, it sends back the
following return telegram.
・
If the recorder receives a command without data request:
ACK (10h, 01h)=Acknowledgement of receipt.
・
If the Recorder receives a command with data request:
Answer code + data
・
If transmission error is detected or undefined command is received:
NAK (11h, 12h) + error code.
Error Code:
Bit 0 (01h)=Command not defined.
Bit 2 (04h)=Checksum error.
Bit 4 (10h)=Parity error.
Bit 5 (20h)=Overrun error.
Bit 6 (40h)=Start/Stop bit error.
Bit 7 (80h)=Time out.
The control system must not send any additional command before having received a
corresponding response to the previous command.
The control system must not interrupt the transmission of a command for more than 10
ms. As soon as the recorder detected such a break longer than 10 ms, it proceeds with
a time out error sequence. The recorder ignores the command received and transmits a
NAK (time out).
As soon as the recorder receives a command from the control system, it sends a return
message within 9 ms. Therefore, unless having a received a return message from the
recorder within 10 ms after execution of a command transmission, the control system
must proceed as if the communication had not taken place under normal
circumstances.
When an error is detected, the recorder immediately sends a NAK to the control system.
Upon receipt of a NAK, the control system in turn must immediately abort the data block
transmission.
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