User`s manual

End Record
Byte Number
1—2 “S9"
3—4 CR,LF.
In the above S records, the byte count includes the load address and
checksum. Thus the byte count is equal to the number of data bytes
plus the following; 3 for S1, 4 for S2 and 5 for S3 type records. The
checksum is the one’s compliment of the 8-bit sum, without carry, of
the byte count, the two bytes of the load address, and the data bytes.
Chapter 7 Hex Formats Model 9000
Page 28