Tab. 30: Response telegram
Length Content
1 byte Number of registers to be trans‐
ferred
n bytes Content of registers requested
3.4.1.4 CRC check sum
The check sum can be calculated with the following tool:
https://www.lammertbies.nl/comm/info/crc-calculation.html
.
3.5 Device monitoring
Device monitoring is only performed if the Modbus is in an active
operating status. To do this, the Modbus master needs to cyclically
send queries to the slaves. If this does not happen - in the speci‐
fied time - the pump stops.
Process:
If queries from the master remain unanswered beyond a certain
time, the pump is stopped. An error message is generated and
transferred to the pump. As soon as queries are resent, the pump
automatically starts up - providing the parameters responsible for
the operation of the pump permit this.
3.6 Emergency mode
You can guard against a potential failure of the Modbus control in
the following way:
1. Set an auxiliary frequency at the pump that ideally fits a
stroke length of 30 ... 100% into your process in emergency
mode.
2. If emergency mode is required, run the pump using the
"external control" terminal on the auxiliary frequency - see
"Operating Instructions for the gamma/ X Solenoid Metering
Pump GMXa" - "Setup".
3.7
Faults
The "Modbus RTU" status LEDs on the Modbus module display
the status of the Modbus connection / Modbus module:
Supplementary Operating Instructions for Modbus RTU
46