Estun ETS-101010APC-CAN - Page 109

ETS Series AC Servo User's Manual
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For example: read 1 word from 01
H
servo address 0201
H
STX
‘：’
ADR
‘0’
‘1’
CMD
‘0’
‘3’
Data start address
‘0’
‘2’
‘0’
‘1’
Data number
（count as word）
‘0’
‘0’
‘0’
‘1’
LRC checking
‘F’
‘8’
End 1
(0D
H
)(CR)
End 0
(0A
H
)(LF)
Add from ADR data to the last data.
01
H
+03
H
+02
H
+01
H
+00
H
+01
H
=08
H
The compensate value is F8
H
when 2 is used to compensate 08
H
, so LRC is “F”,”8”.
CRC calculation of RTU mode:
RTU mode uses CRC (Cyclical Redundancy Check) error detection value.
The process of CRC error detection value calculation is shown as follows:
Step 1: Load in a 16-bit register of FFFF
H
, named “CRC” register.
Step 2: Run XOR calculation between the first bit (bit 0) of instruction information and 16-bit CRC register’s low bit (LSB),
and the result is saved to CRC register.
Step 3: Check the lowest bit (LSB) of CRC register, if it is 0, CRC register moves one bit to right; if it is 1, CRC register
moves one bit to right, then run XOR calculation with A001
H
;
Step 4: Go to step 5 till the third step has been executed for 8 times, otherwise return to step 3.
Step 5: Repeat the steps from 2 to 4 for the next bit of instruction information, the comment of CRC register is the CRC
error detection value while all the bits have been executed by the same way.
Note: After calculating out the CRC error detection value, the CRC low bit should be filled first in instruction information,
and then fill the high bit of CRC.
Please refer to the following example:
Read 2 words from the 0101
H
address of 01
H
servo. The final CRC register content calculated from ADR to the last bit of
data is 3794
H
, and then the instruction information is shown as follows,
Please be sure that 94
H
is transmitted before 37
H
.
ADR
01
H
CMD
03
H
Data start address
01
H
(high-bit)
01
H
(low-bit)
Data number
（count as word）
00
H
(high-bit)
02
H
(low-bit)
CRC checking
94
H
(low-bit)
CRC checking
37
H
(high-bit)
End1、End0（Communication is complete.）