ES58 • EM58 MODBUS®
The full frame needed for the request to read the
parameter (registers 5 and 6) to the Slave having the node address 1 is as
follows:
Request PDU
(in hexadecimal format)
[01][03][00][04][00][02][85][CA]
where:
[01] = Slave address
[03] =
function code
[00][04] = starting address (
5)
[00][02] = number of requested registers
[85][CA] = CRC
The full frame needed to send back the values of the
parameter (registers 5 and 6) from the Slave having the node address 1 is
as follows:
Response PDU
(in hexadecimal format)
[01][03][04][00][00][05][DC][F8][FA]
where:
[01] = Slave address
[03] =
function code
[04] = number of bytes (2 bytes for each register)
[00][00] = value of register 5, 00 00 hex = 0 dec
[05][DC] = value of register 6, 05 DC hex = 1500 dec
[F8][FA] = CRC
04 Read Input Register
FC = 04 (04 hex)
This function code is used to READ from 1 to 125 contiguous input registers in a
remote device; in other words, it allows to read some results values and state /
alarm messages in a remote device. The Request PDU specifies the starting
register address and the number of registers. In the PDU registers are addressed
starting at zero. Therefore input registers numbered 1-16 are addressed as 0-15.
The register data in the response message are 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 input registers accessible using
function code please refer to the “7.1.2 Input Register parameters” section on
page 76.
MAN ESx58x_EMx58x MB E 1.3
MODBUS® interface
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