Motorola M68EVB912B32, User Manual

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S-RECORD FORMAT
68EVB912B32UM/D A-1
APPENDIX A
S-RECORD FORMAT
DESCRIPTION
The S-Record format for output modules was devised for the purpose of encoding programs or
data files in a printable format for transportation between computer systems. The transportation
process can thus be visually monitored and the S-Records can be more easily edited.
S-RECORD CONTENT
When viewed by the user, S-Records are essentially character strings made of several fields that
identify the record type, record length, memory address, code/data, and checksum. Each byte of
binary data is encoded as a 2-character hexadecimal number: the first character represents the
high-order 4 bits, and the second represents the low-order 4 bits of the byte.
The 5 fields that comprise an S-Record are shown below:
TYPE RECORD LENGTH ADDRESS CODE/DATA CHECKSUM
The S-Record fields are composed as follows:
Field Printable
Characters
Contents
Type 2 S-Record type - S0, S1, etc.
Record length 2 The count of the character pairs in the record, excluding the type and
record length.
Address 4, 6, or 8 The 2-, 3-, or 4-byte address at which the data field is to be loaded into
memory.
Code/data 0-2n From 0 to n bytes of executable code, memory-loadable data, or
descriptive information. For compatibility with teletypewriters, some
programs may limit the number of bytes to as few as 28 (56 printable
characters in the S-Record).
Checksum 2 The least significant byte of the one’s complement of the sum of the
values represented by the pairs of characters making up the record
length, address, and the code/data fields.