Motorola M68CPU32BUG Manuel d'utilisateur télécharger pdf (Page 85)

S-RECORD INFORMATION

M68CPU32BUG REV 1 A-4

The next 16 character pairs of the first S1 record are the ASCII bytes of the actual program

code/data. In this assembly language example, the hexadecimal opcodes of the program are

written in sequence in the code/data fields of the S1 records:

OPCODE INSTRUCTION

285F MOVE.L (A7)+,A4

245F MOVE.L (A7)+,A2

2212 MOVE.L (A2),D1

226A0004 MOVE.L 4(A2),A1

24290008 MOVE.L FUNCTION(A1),D2

237C MOVE.L #FORCEFUNC,FUNCTION(A1)

(The balance of this code is continued in the code/data fields of the remaining S1

records and stored in memory.)

2A The checksum of the first S1 record.

The second and third S1 records also each contain $13 (19) character pairs and are ended with

checksums 13 and 52 respectively. The fourth S1 record contains 07 character pairs and has a

checksum of 92.

The S9 record is explained as follows:

S9 S-record type S9, indicating that it is a termination record.

03 Hexadecimal 03, indicating that three character pairs (3 bytes) follow.

00 The address field, zeros.

FC The checksum of the S9 record.

Each printable character in an S-record is encoded in a hexadecimal (ASCII in this example)

representation of the binary bits which are actually transmitted. For example, the first S1 record

above is sent as:

0101 0011 0011 0001 0011 0001

TYPE

0011 0011 0011 0000 0011 0000 0011 0000 0011 0000 0011 0010 0011 1000 0011 0101 0100 0110 ••• 0011 0010 0100 0001

533131 33030303032383546•••3241

S1130000285F•••2A

LENGTH ADDRESS CODE/DATA CHECKSUM

S-RECORD INFORMATION

M68CPU32BUG REV 1 A-1

APPENDIX A

S-RECORD INFORMATION

A.1 INTRODUCTION

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.

A.2 S-RECORD CONTENT

When viewed by the user, S-records are essentially character strings made of several fields which

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 representing the

high-order 4 bits, and the second the low-order 4 bits of the byte.

The five fields which comprise an S-record are shown below:

TYPE RECORD LENGTH

ADDRESS

CODE/DATA

CHECKSUM

Where the fields are composed as follows:

Field

Printable

Characters Contents

type 2 S-records type -- S0, S1, etc.

record length 2 The count of the character pairs in the record, excluding 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-n 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 records

length, address, and the code/data fields.

eescale S

emiconduct

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Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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Motorola M68CPU32BUG Manuel d'utilisateur Page 85

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