User Manual

2 Protocol description

2.4.2 Communication during the internal processing time of the slave

No data requests from the master are permitted during the internal

processing time. Any data requests that are made during this period will

be ignored by the slave.

2.4.3 Communication during the response time of the slave

No data requests from the master are permitted during the response

time of the slave. Any data requests that are made during this period will

result in the invalidation of all the data currently on the bus.

2.5 Structure of the data blocks

All data blocks have the same structure:

Data structure

Each data block contains four fields:

Slave address device address of a specific slave

Function code Function selection (read, write words)

Data field contains the information:

- word address

- word number

- word value

Checksum detection of transmission errors

2.6 Error handling

Error codes There are three error codes:

1 invalid function

2 invalid parameter address

8 write access to parameter denied

Slave

address

Function

code

Data field Checksum

CRC16

1 byte 1 byte x byte(s) 2 bytes