Function Codes; Function Code List; 03 Hex: Reading Of Multiple Registers - Omron S8VK-X Communications Manual

4-2

Function Codes

This section describes function codes that can be used with Modbus TCP.
4-2-1

Function Code List

The function codes that can be used are as follows.
Function code
03 hex
06 hex
10 hex
4-2-2

03 hex: Reading of multiple registers

This function can read the contents of multiple registers starting from the specified address.
Frame configurations
The frame configurations of ModbusTCP are as follows.
 Request
(1)
00 00
2
(1): Transaction ID
(2): Protocol ID
(3): Number of bytes transferred
(4): Unit ID
(5): Function code
(6): Start address
(7): Number of words to read
Switch-mode Power Supplies Communications Manual (T213)
4 Monitoring and Setting with the Modbus TCP
Function name
Reading of multiple registers
Operation command
Writing of multiple registers
(2) (3)
00 00 00 06
2 2
: Specify any value. For example, 0000 hex is used in this explanation.
: Specify 0000 hex.
: Specify the total number of bytes of (4) and the successor.In the above
case, it is from (4) to (7), so it is 0006 hex.
: Specify FF hex.
: Specify 03 hex (Reading of multiple registers).
: Specify the address to start reading.
Refer to 4-3 Register Address Lists on page 4-8.
: Specify the number of words of the register to be read. The maximum
value is 32 (0020 hex).
Usages
Used to read output voltage, IP address, etc.
Used to reset the peak hold current.
Used to set the IP address, etc.
(4) (5) (6)
FF 03
1 1 2
(7)
Hex
Bytes
2
4 - 3
4