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15. ABSOLUTE POSITION DETECTION SYSTEM
(c) Checksum
The check sum is the code which is used by the programmable controller to check for errors in the
received ABS data. The 6-bit check sum 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 check sum code sent from the servo.
The method of calculating the check sum 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 check sum
is 6-bit data.
Negative data is available for the FX-1PG and unavailable for the A1SD71.
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 check sum of " 10" (ABS data) is "2D
b
"