43
4-2-6.
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.
