Hitachi CP-X200 Instruction Manual page 252

No response occurs:
In the cases below, the inverter ignores a query and returns no response.
When receiving a broadcasting query
When detecting a transmission error in reception of a query
When the slave address set in the query is not equal to the slave address of the
inverter
When a time interval between data elements constituting a message is shorter than
3.5 characters
When the data length of the query is invalid
NOTE: Provide a timer in the master and make the master retransmit the same query
when no response is made within a preset time period after the preceding query was
sent.
B − 9
B 9