Lika EMC58 MT, User Manual

Page: 39 / 104

EM58 – HS58 - HM58 MODBUS TCP/IP
6.5.1 Implemented function codes
Lika MODBUS TCP/IP encoders only implement public function codes, they are
described hereafter.
03 Read Holding Registers
FC = 03 (0003 hex) ro
This function code is used to READ the contents of a contiguous block of
Holding Registers (4X Reference Addresses) in a remote device; in other words, it
allows to read the values set in a group of work parameters placed in order. The
Request PDU specifies the starting register address and the number of registers.
In the PDU registers are addressed starting at zero. Therefore registers
numbered 1-16 are addressed as 0-15.
The register data in the response message is packed as two bytes per register,
with the binary contents right justified within each byte. For each register, the
first byte contains the high order bits (msb) and the second contains the low
order bits (lsb).
For the complete list of the holding registers accessible using the
03 Read
Holding Registers
function code please refer to the “7.1.1 Holding Register
parameters” section on page 51.
Request PDU
Function code 1 byte 0003 hex
Starting address 2 bytes 0000 hex to FFFF hex
Quantity of registers 2 bytes 1 to 125 (007D hex)
Response PDU
Function code 1 byte 0003 hex
Byte count 1 byte
2 x
N*
Register value N* x 2 bytes
*N = Quantity of registers
Exception Response PDU
Error code 1 byte
0083 hex (=0003 hex +
0080 hex)
Exception code 1 byte 01 or 02 or 03 or 04
MAN EM58_HS58_HM58 MT E 1.1.odt MODBUS® TCP/IP interface 39 of 104