LCD C-DESK-BR User Manual page 54

For additional information on this protocol refer to the general technical specifications
PI_MBUS_300.
In general queries and answers toward and from one slave instrument are composed as follows:
FUNCTION 3: Read holding registers (READ PROGRAMMABLE REGISTERS)
QUERY
Address
A
Tot. byte = 8
RESPONSE
Address Function
A
Tot. byte = 3+2*No. registers+2
where: No. registers... number of Modbus registers to write beginning from the address no. 1
No. byte ........ number of bytes of the following data
FUNCTION 16: Preset multiple registers (WRITE MULTIPLE REGISTERS)
QUERY
Address Function 1st reg. add.
A 0x10
Tot. byte = 7+2*No. registers+2
RESPONSE
Address
A
Tot. byte = 8
where: No. registers... number of Modbus registers to read beginning from the address no. 1
No. byte ........ number of bytes of the following data
Val.reg.1 ....... contents of the register beginning from the first
The response contains the number of registers modified beginning from the address no. 1.
Function
0x03
No. bytes
0x03 0x04
No. reg.
0x0000 0x0002
Function 1st reg. address
0x10
1st register address
0x0000
1st register
0x0064
No. bytes Val.reg.1
0x04 0x0000
No. reg.
0x0000
- 49 -
No. registers
0x0002
2nd register
0x00C8
Val.reg.2
0x0000
2 byte
0x0002 CRC
2 byte
CRC
2 byte
CRC
2 byte
CRC