Siemens SIMPRO-100 - Modbus Function Codes: Status and Diagnostics; 07 h Read Exception Status Command; 08 h Loopback Diagnostic Command

C
Modbus
™
RTU Communications Protocol
SIMPRO-100
162 PRIM-2400C
C.5 03h Read Holding
Registers Command
Use function code 03h to read directly from the
Modbus Register map shown in Table C.19 on
page 187. You may read a maximum of 125
registers at once with this function code. Most
masters use 4X references with this function
code. If you are accustomed to 4X references
with this function code, for 5-digit addressing, add
40001 to the standard database address.
Table C.6 03h Read Holding Registers Command
C.6 04h Read Input
Registers Command
Use function code 04h to read from the Modbus
map shown in Table C.19 on page 187. You may
read a maximum of 125 registers at once with this
function code.
Table C.7 04h Read Input Registers Command
Bytes Field
The Master Request must have the Following
Format
1 byte Slave address
1 byte Function code (03h)
2 bytes Starting register address
2 bytes Number of registers to read
2 bytes CRC-16 for message
A Successful SIMPRO-100 Relay Response will
have the Following Format
1 byte Slave address
1 byte Function code (03h)
1 byte
Byte count (should be twice the number of
registers read)
n bytes Byte count bytes of data
2 bytes CRC-16 for message
Bytes Field
The Master Request must have the Following
Format
1 byte Slave address
1 byte Function code (04h)
2 bytes Starting register address
2 bytes Number of registers to read
2 bytes CRC-16 for message
A Successful SIMPRO-100 Relay Response will
have the Following Format
1 byte Slave address
1 byte Function code (04h)
1 byte
Byte count (should be twice the number of
registers read)
n bytes Byte count bytes of data
2 bytes CRC-16 for message