www.Siargo.com
MF4700
User
Manual
20
|
P a g e
5.5.3.
Frame
The
frame
function
is
based
on
the
standard
Modbus
RTU
framing:
Table
5.4:
frame
function
Start_bits
Address
Function
codes
Data
CRC
Stop_bits
T1
‐
T2
‐
T3
‐
T4
8
bit
8
bit
N
8
bit
(20
≥
n
≥
0)
16
bit
T1
‐
T2
‐
T3
‐
T4
Start_bits
:
4
periods
bit
time,
for
a
new
frame.
Address:
The address can be set from 1 to 255 except for 157 (0x9d). 0 is the broadcast address.
Function codes:
Define the product (MF4700)'s functions/actions (slaves), either execution or response.
Data:
The address of the register, length of data, and the data themselves.
CRC:
CRC verification code. The low byte is followed by the high byte. For example, a 16 bit
CRC is divided into BYTE_H and BYTE_L. In the framing, the BYTE_L will come first, then
followed by the BYTE_H. The last one is the STOP signal.
Stop_bits:
4 periods bit time, for ending the current frame.
5.5.4.
Function
codes
The
Modbus
function
codes
applied
for
the
product
are
the
sub
‐
class
of
the
standard
Modbus
function
‐
codes.
These
codes
are
used
to
set
or
read
the
registers
of
the
product:
Table
5.5:
function
codes
Code
Name
Functions
0x03
Read
register
Read
register(s)
0x06
Set
single
register
Write
one
single
16
‐
bit
register
0x10
Set
multiple
registers
Write
multiple
registers