Read Holding Registers Command (0X03) - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

Field Name
Number of coils to read (high)
Number of coils to read (low)
Error Check (CRC) byte 1
Error Check (CRC) byte 2
Response Details
Table 3-25 Read Coils Response (RX) from Master
Field Name
Slave Address
Function
Data from coils
Data from coils
Data from coils
Data from coils
Data from coils
Error Check (CRC) byte 1
Error Check (CRC) byte 2
*The response includes data that is decoded as follows:
● Data is packed with 1 bit for each coil (1 = ON, 0 = OFF).
● The low order bit of the first character contains the addressed coil. The remainder bits follow.
● For coil quantities that are not even multiples of 8, the last characters are filled in with zeros
at high order end.
● The status of coils 20-27 is shown as CD (HEX) = 1100 1101 (binary). Reading left to right,
this shows that coils 27, 26, 23, 22, and 20 are all on. The other coil data bytes are decoded
similarly.
● Due to the quantity of coil statuses requested, the last data field, shown as 1B (HEX) = 001
1011 (binary), contains the status of only 5 coils (52-56) instead of 8 coils. The 3 left-most
bits are provided as zeros to fill the 8-bit format.
3.5.2

Read Holding Registers Command (0x03)

Description
The "read holding registers" command allows the Modbus master to read up to 64 consecutive
memory registers from the drive.
NXGpro Communication
Function Manual, AB, A5E33486415A
Value (in Hex)
0x00
0x25
—
—
Value (in Hex)
0x01
0x01
0xCD
0x6B
0x02
0x0E
0x1B
—
—
Modbus Communication
Description
Read 37 coils starting from coil 20
Byte 1 of CRC for this message
Byte 2 of CRC for this message
Description
0x01 = 1 decimal
Read coils command
Decoded data from coils*
Decoded data, high bits are filled with
zeros if no data requested
Byte 1 of CRC for this message
Byte 2 of CRC for this message
3.5 Functions
65