Handeingabegerät
Handbediengerät mit serieller Schnittstelle
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MR 175 Handheld Pendant, Manual
The MR175 transmits a full transmission packet upon power up, and upon change in state.
Following any transmission, the MR175 will wait for 120ms for a response. If the host does not
respond within 120ms a second updated (new) transmission packet is sent.
If the response is “C”, unit waits for more user input and sends the next packet when
appropriate.
If the response is “E”, unit transmits the last packet and continues monitoring user input.
If no response occurs within 120ms, or a response is received other than “c” or “e”, the MR175
will modify the last transmitted packet as follows, and send the updated packet:
The start of transmission byte is then as ASCII “S” indicating a second attempt.
The packet number shall be incremented by one.
Incoming invalid characters are reported as Error 5, invalid command. Cr, LF are discarded
without error.
Exceptions
Transmission Errors:
The RS-485 peer to peer link is very robust and errors are unlikely to occur. In the case
transmission errors do occur, it can be recognized by the host when testing the two-byte
checksum. The best remedy for an erroneous packet is to request a repeat packet by sending
command
“e”
.
An unrecognized command received by the MR175 will be reported as “Error: 5 Invalid
Command”. The exception is that CR/LF are simply ignored.
