Virtual I/O Commands - ICP DAS USA PDS-700 User Manual

8. Virtual I/O Commands

Command Format: (Leading)(Address)(Command)[CHK](cr)
Response Format: (Leading)(Address)(Data)[CHK](cr)
2-character, "01" for PDS virtual I/O
(Address)
2-character checksum, no checksum for PDS virtual I/O
[CHK]
carriage return (0x0D) for ending character of command
(cr)
Checksum Calculation:
1. Calculate the ASCII sum of all characters in the command (or response) string except
for the return character (cr).
2. Mask the sum of the string with 0ffh
Example:
Command string: $012 (cr)
Sum of the string = '$' + '0' + '1' + '2' = 24 h + 30 h + 31 h + 32 h = B7 h
The checksum is B7 h, and [CHK] ="B7".
Command string with checksum: $012B7 (cr)
Response string: !01300600 (cr)
Sum of the string = '!' + '0' + '1' + '3' + '0' + '0' + '6' + '0' + '0'
= 21 h + 30 h + 31 h + 33 h + 30 h + 30 h + 36 h + 30 h + 30 h = 1AB h
The checksum is AB h, and [CHK] ="AB".
Response string with checksum: !01300600AB (cr)
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