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14. ABSOLUTE POSITION DETECTION SYSTEM
(c) Checksum
The checksum is the code which is used by the programmable controller to check for errors in the
received ABS data. The 6-bit checksum is transmitted following the 32-bit ABS data.
At the programmable controller, calculate the sum of the received ABS data using the ladder program
and compare it with the checksum code sent from the servo.
The method of calculating the checksum is shown. Every time the programmable controller receives 2
bits of ABS data, it adds the data to obtain the sum of the received data. The checksum is 6-bit data.
Example: ABS data:
10 (FFFFFFF6H)
10
b
01
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
11
b
b
11
101101
b
10
FFFF FFF6
1111 1111 1111 0110
<Appendix>
Decimal
Hexadecimal
Binary
When the binary data of each 2bits of the
ABS data is added up, "10 1101 " is obtained.
b
Therefore, the checksum of "
10" (ABS data) is "2D
b
"