Each record starts with a record type which indicates the type of the record, and record length which contain the number of bytes in the record exclusive of the first two fields. The record ends with a checksum byte which contains the 2s complement of the sum (modulo 256) of all other bytes in the record. Therefore the sum (modulo 256) of all bytes in the record is zero.

The record length includes the payload and checksum fields, but excludes the type and length fields.

All 16-bit fields are little-endian. tab(;),center,allbox; cw(0.4i) cw(0.8i) cw(1.6i) cw(0.4i). T{ REC TYP

8 bits T};T{ Record Length

16 bits T};T{ Payload T};T{ CHK SUM

8 bits T}

Here are some of the relevant record types: tab(;),center; l l. 0x01;Scope Definition Record 0x02;Module Start Record 0x04;Module End Record 0x06;Content Record 0x0E;Segment Definition Record 0x12;Debug Items Record 0x16;Public Definition Record 0x18;External Definition Record

Names are not stored a C strings. Names are stored as a length byte followed by the contents.

An AOMF file consists of a module header record (0x02), followed by one or more content (0x06), scope (0x01) or debug (0x12) records, and ends in a module end record (0x04).

The records with the following types are extraneous (they may appear in the file but are ignored): 0x0E, 0x16 and 0x18 (definition records). All records which are not part of the AOMF and are not extraneous are considered erroneous.

tab(;),center,allbox; cw(0.4i) cw(0.8i) cw(1.2i) cw(0.4i) cw(0.4i) cw(0.4i). T{ REC TYP

0x02 T};T{ Record Length

16 bits T};T{ Module Name T};T{ TRN ID

8 bits T};T{ zero

8 bits T};T{ CHK SUM

8 bits T}

Each module must starts with a module header record. It is used to identify the module for the RL51 and other future processors of 8051 object files. In addition to the Module Name the record contains:

TRN ID

The byte identifies the program which has generated this module: tab(;),center; l l. 0xFD;ASM51 0xFE;PL/M-51 0xFF;RL51.

tab(;),center,allbox; cw(0.4i) cw(0.8i) cw(1.2i) cw(0.8i) cw(0.4i) cw(0.4i) cw(0.4i). T{ REC TYP 0x04 T};T{ Record Length

16 bits T};T{ Module Name T};T{ zero

16 bits T};T{ REG MSK

8 bits T};T{ zero

8 bits T};T{ CHK SUM

8 bits T}

The record ends the module sequence and contains the following information: characteristics

MODULE NAME

The name of the module is given here for a consistency check. It must match the name given in the Module Header Record.

REGISTER MASK (REG MSK)

The field contains a bit for each of the four register banks. Each bit, when set specifies that the corresponding bank is used by the module:

Bit 0 (the least significant bit)

bank #0.

Bit 1

bank #1.

Bit 2

bank #2.

Bit 3

bank #3.

tab(;),center,allbox; cw(0.4i) cw(0.8i) cw(0.4i) cw(0.8i) cw(1.2i) cw(0.4i). T{ REC TYP

0x06 T};T{ Record Length

16 bits T};T{ SEG ID

8 bits T};T{ Offset

16 bits T};T{ DATA T};T{ CHK SUM

8 bits T}

This record provides one or more bytes of contiguous data, from which a portion of a memory image may be constructed.

SEG ID

This field must be zero.

OFFSET

Gives the absolute address of the first byte of data in the record, within the CODE address space.

DATA

A sequence of data bytes to be loaded from OFFSET to OFFSET+RECORDLENGTH-5.

In general, raw binary data will expand in sized by approximately 1.02 times when represented with this format.