Shihlin electric SDP Series, Manual

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Example 3 : function code 10H, writing multiple words.
Write the data of 2 byte groups 0BB8H and 0000H to the starting address 0112H of the servo
drive with device number 01H, that is, 0BB8H is written to 0112H and 0000H is written to 0113H.
The maximum allowable data in one single access is 10.
Command message(Host) Response message(Slave)
ADR 01H ADR 01H
CMD 10H CMD 10H
Start data
address
01H(
high byte)
Start data
address
01H(
high byte)
12H(
low byte)
12H(
low byte)
Data quantity
(word)
00H(
high byte)
Data quantity
00H(
high byte)
02H(
low byte)
02H(
low byte)
Data
quantity(byte)
04H
CRC Check
(low byte)
E0H(
low byte)
Content of the 1
st Data
0BH(
high byte)
CRC Check
(high byte)
31H(
high byte)
B8H(
low byte)
Content of the
2nd Data
00H(
high byte)
00H(
low byte)
CRC Check
(low byte)
FCH(
low byte)
CRC Check
(high byte)
EBH(
high byte)
CRC error check value calculation(RTU mode) :
The error check in RTU mode is CRC(Cyclical Redundancy Check).
The CRC error detection value calculation is explained in the following steps:
Step 1: load a 16-bit register with the content of FFFFH, which is called the “CRC” register.
Step 2: perform Exclusive OR calculation between the first byte of the command message and
the 16-bit CRC register, and then save the result in the CRC register.
Step 3: check the least significant bit (LSB) of the CRC register. If the bit is 0, shift the register
one bit to the right. If the bit is 1, shift the register one bit to the right and execute Exclusive OR
calculation between the CRC register and A001H.
Step 4: repeat step 3 for 8 times and then go to step 5.
Step 5: repeat steps 2 and 4 until all bytes have been processed. The content of the CRC
register is the CRC value.