Table 3-8 Calculating The Checksum Procedure - Honeywell UDC2300 Product Manual

3.7 Checksum Protocol (for Data Security),
Calculating the
Checksum
28 RS422/485 ASCII Communications Option Product Manual
Table 3-8 lists the procedure for calculating the checksum. See Figure 3-5
for an example.
Table 3-8 Calculating the Checksum Procedure
Step
1 Take the binary sum, ignoring carries generated by the most
significant bits, of the ASCII code for each of the message's
characters, ignoring parity, up to but not including the CHECKSUM
field and the CR and LF characters. The final sum should be an 8-bit
binary number. See Section 7 for ASCII Conversion table and
Hexadecimal to Binary table.
2 Convert the four least significant bits of this sum to the equivalent
hexadecimal digit. This becomes the least significant digit in the
CHECKSUM field.
3 Convert the four most significant bits of this sum to the equivalent
hexadecimal digit. This becomes the most significant digit in the
checksum field.
Continued
Action
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