Saci SAM3001 Serie Manual De Usuario página 89

12.1 Communication
12.1.1 Physical layer
The communication interface of SAM3001 should be connected by shielded
twisted pair. A bus can connect 32 devices at most and terminal resistance
should be connected at both ends of the bus. Communication speed range is
1200～19200bps，defaulted as 19200bps; Byte format is 1 start bit, 8 data
bits, no check bit or 1 odd/even check bit, and 1/2 stop bit.
12.1.2 Communication Protocol
Data format
Address code
one byte
Address code: slave address; address range 1-247, other addresses are
reserved. When the module address is not known, the address information
of the M module can be read by the address 255 broadcast.
Function code: It tells the addressed terminal device to perform a function.
The following list shows the function codes supported by the device as well
as corresponding meaning and functions.
Function code
0x01
0x02
SAM3001 Manual de usuario V5
Function code
one byte
Meaning
Read the status of relay output
Read the status of digital input
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Data code
N bytes
CRC check code
two bytes