Inovance H3U Series - Page 606

605
9
9 Communication 9.4.3 Modbus Parameter Numbers and Data Addressing
Incorrect response: See "g) Incorrect response frame".
• N: The
H3U
PLC can read a maximum of 255 coils at a time.
b) Parameter number 0x03 (03): Reads registers.
Request frame format: slave address + 0x03 + head address of registers + number of registers + CRC
code
No.
Denition of Data
(Byte)
Number of
Bytes
Description
1 Slave address 1
The value ranges from 1 to 247, set by
D8121.
2
0x03 (parameter
number)
1 The instruction is to read registers.
3
Head address of
registers
2
Upper bits are followed by lower bits. See
"Register addressing".
4
Number of
registers
2 Upper bits are followed by lower bits (N).
5 CRC code 2 Upper bits are followed by lower bits.
Response frame format: slave address + 0x03 + number of bytes + register value + CRC code
No.
Denition of Data
(Byte)
Number of
Bytes
Description
1 Slave address 1 The value ranges from 1 to 247, set by D8121.
2
0x03 (parameter
number)
1 The instruction is to read registers.
3 Number of bytes 1 The value is N x 2
4 Register value N x 2
One register value is indicated by two bytes.
Upper bits are followed by lower bits. The
register with a smaller address is indicated by
the rst byte.
5 CRC code 2 Upper bits are followed by lower bits.
Incorrect response: See "g) Incorrect response frame".
• N: The H3U PLC can read a maximum of 125 registers at a time.