The Intel HEX file is an ASCII text file with lines of
text that follow the Intel HEX file format. Each line in an Intel HEX file
contains one HEX record. These records are made up of hexadecimal numbers that
represent machine language code and/or constant data. Intel HEX files are often
used to transfer the program and data that would be stored in a ROM or EPROM.
Most EPROM programmers or emulators can use Intel HEX files.
Record Format
An Intel HEX file is composed of any number of HEX
records. Each record is made up of five fields that are arranged in the
following format:
:llaaaatt[dd...]cc
Each group of letters corresponds to a different field,
and each letter represents a single hexadecimal digit. Each field is composed
of at least two hexadecimal digits-which make up a byte-as described below:
- : is
the colon that starts every Intel HEX record.
- ll is
the record-length field that represents the number of data bytes (dd)
in the record.
- aaaa is
the address field that represents the starting address for subsequent data
in the record.
- tt is
the field that represents the HEX record type, which may be one of the
following:
00 - data record
01 - end-of-file record
02 - extended segment address record
04 - extended linear address record
05 - start linear address record (MDK-ARM only) - dd is
a data field that represents one byte of data. A record may have multiple
data bytes. The number of data bytes in the record must match the number
specified by the ll field.
- cc is
the checksum field that represents the checksum of the record. The
checksum is calculated by summing the values of all hexadecimal digit
pairs in the record modulo 256 and taking the two's complement.
Data Records
The Intel HEX file is made up of any number of data
records that are terminated with a carriage return and a linefeed. Data records
appear as follows:
:10246200464C5549442050524F46494C4500464C33
This record is decoded as follows:
:10246200464C5549442050524F46494C4500464C33
||||||||||| CC->Checksum
|||||||||DD->Data
|||||||TT->Record Type
|||AAAA->Address
|LL->Record Length
:->Colon
where:
- 10 is
the number of data bytes in the record.
- 2462 is
the address where the data are to be located in memory.
- 00 is
the record type 00 (a data record).
- 464C...464C is
the data.
- 33 is
the checksum of the record.
Extended Linear Address Records (HEX386)
Extended linear address records are also known as
32-bit address records and HEX386 records. These records contain the upper 16
bits (bits 16-31) of the data address. The extended linear address record
always has two data bytes and appears as follows:
:02000004FFFFFC
where:
- 02 is
the number of data bytes in the record.
- 0000 is
the address field. For the extended linear address record, this field is
always 0000.
- 04 is
the record type 04 (an extended linear address record).
- FFFF is
the upper 16 bits of the address.
- FC is
the checksum of the record and is calculated as
01h + NOT(02h + 00h + 00h + 04h + FFh + FFh).
When an extended linear address record is read, the
extended linear address stored in the data field is saved and is applied to
subsequent records read from the Intel HEX file. The linear address remains
effective until changed by another extended address record.
The absolute-memory address of a data record is
obtained by adding the address field in the record to the shifted address data
from the extended linear address record. The following example illustrates this
process..
Address from the data record's address field 2462
Extended linear address record data field FFFF
--------
Absolute-memory address FFFF2462
Extended Segment Address Records (HEX86)
Extended segment address records-also known as HEX86
records-contain bits 4-19 of the data address segment. The extended segment
address record always has two data bytes and appears as follows:
:020000021200EA
where:
- 02 is
the number of data bytes in the record.
- 0000 is
the address field. For the extended segment address record, this field is
always 0000.
- 02 is
the record type 02 (an extended segment address record).
- 1200 is
the segment of the address.
- EA is
the checksum of the record and is calculated as
01h + NOT(02h + 00h + 00h + 02h + 12h + 00h).
When an extended segment address record is read, the
extended segment address stored in the data field is saved and is applied to
subsequent records read from the Intel HEX file. The segment address remains
effective until changed by another extended address record.
The absolute-memory address of a data record is
obtained by adding the address field in the record to the shifted-address data
from the extended segment address record. The following example illustrates
this process.
Address from the data record's address field 2462
Extended segment address record data field 1200
--------
Absolute memory address 00014462
Start Linear Address Records (MDK-ARM only)
Start linear address records specify the start address
of the application. These records contain the full linear 32 bit address. The
start linear address record always has four data bytes and appears as follows:
:04000005000000CD2A
where:
- 04 is
the number of data bytes in the record.
- 0000 is
the address field. For the start linear address record, this field is
always 0000.
- 05 is
the record type 05 (a start linear address record).
- 000000CD is
the 4 byte linear start address of the application.
- 2A is
the checksum of the record and is calculated as
01h + NOT(04h + 00h + 00h + 05h + 00h + 00h + 00h + CDh).
The Start Linear Address specifies the address of the
__main (pre-main) function but not the address of the startup code which
usually calls __main after calling SystemInit(). An odd linear start address
specifies that __main is compiled for the Thumb instruction set.
The Start Linear Address Record can appear anywhere in
hex file. In most cases this record can be ignored because it does not contain
information which is needed to program flash memory.
End-of-File (EOF) Records
An Intel HEX file must end with an end-of-file (EOF)
record. This record must have the value 01 in the record type field. An EOF
record always appears as follows:
:00000001FF
where:
- 00 is
the number of data bytes in the record.
- 0000 is
the address where the data are to be located in memory. The address in
end-of-file records is meaningless and is ignored. An address of 0000h is
typical.
- 01 is
the record type 01 (an end-of-file record).
- FF is
the checksum of the record and is calculated as
01h + NOT(00h + 00h + 00h + 01h).
Example Intel HEX File
Following is an example of a complete Intel HEX file:
:10001300AC12AD13AE10AF1112002F8E0E8F0F2244
:10000300E50B250DF509E50A350CF5081200132259
:03000000020023D8
:0C002300787FE4F6D8FD7581130200031D
:10002F00EFF88DF0A4FFEDC5F0CEA42EFEEC88F016
:04003F00A42EFE22CB
:00000001FF
