VIPA CPU 312SC - Page 160

The description always takes place from the point of view of the
master. Here data, which were sent from master to slave, up to their
target are designated as "output" data (OUT) and contrary slave data
received by the master were designated as "input" data (IN).
If the slave announces an error, the function code is send back with
an "ORed" 80h.
Without an error, the function code is sent back.
Slave answer: Function code OR 80h ® Error
Function code ® OK
1 word
High-byte Low-byte
The shown check sums CRC at RTU and LRC at ASCII mode are
automatically added to every telegram. They are not shown in the
data block.
Code 01h: Read n bits of master output area 0x
Code 02h: Read n bits of master input area 1x
Command telegram
Slave address Function code Address 1. bit Number of bits Check sum CRC/
LRC
1byte 1byte 1word 1word 1word
Respond telegram
Slave
address
Function
code
Number of
read bytes
Data 1.
byte
Data 2.
byte
... Check sum
CRC/LRC
1byte 1byte 1byte 1byte 1byte 1word
max. 250byte
Respond of the slave
Byte sequence in a
word
Check sum CRC, RTU,
LRC
Read n bits 01h, 02h
VIPA System 300SDeployment PtP communication
Modbus - Function codes
HB140 | CPU-SC | 312-5BE13 | GB | 15-50 160