More data inspection

IntelHex provides some metadata about the hex file it contains. To obtain address limits use methods .minaddr() and .maxaddr(). These are computed based on the lowest and highest used memory spaces respectively.

Some linkers write to produced HEX file information about start address (either record 03 or 05). IntelHex is able correctly read such records and store information internally in start_addr attribute that itself is either None or a dictionary with the address value(s).

When input HEX file contains record type 03 (Start Segment Address Record), start_addr takes value:

{'CS': XXX, 'IP': YYY}


  • XXX is value of CS register
  • YYY is value of IP register

To obtain or change CS or IP value you need to use their names as keys for start_addr dictionary:

>>> ih = IntelHex('file_with_03.hex')
>>> print ih.start_addr['CS']
>>> print ih.start_addr['IP']

When input HEX file contains record type 05 (Start Linear Address Record), start_addr takes value:

{'EIP': ZZZ}

Here ZZZ is value of EIP register.


>>> ih = IntelHex('file_with_05.hex')
>>> print ih.start_addr['EIP']

You can manually set required start address:

>>> ih.start_addr = {'CS': 0x1234, 'IP': 0x5678}
>>> ih.start_addr = {'EIP': 0x12345678}

To delete start address info give value None or empty dictionary:

>>> ih.start_addr = None
>>> ih.start_addr = {}

When you write data to HEX file you can disable writing start address with additional argument write_start_addr:

>>> ih.write_hex_file('out.hex') # by default writing start address
>>> ih.write_hex_file('out.hex', True) # as above
>>> ih.write_hex_file('out.hex', False) # don't write start address

When start_addr is None or an empty dictionary nothing will be written regardless of write_start_addr argument value.

For more information about start address, please see the Intel Hex file format specification.

Because Intel Hex files do not specify every location in memory, it is necessary to have a padding byte defined. Whenever a read is attempted from an address that is unspecified, the padding byte is returned. This default data is set via attribute .padding of class instance. This defaults to ‘0xFF’, but it can be changed by the user like so:

>>> print ih[0]       # prints 0xFF because this location is blank
>>> ih.padding = 0x00 # change padding byte
>>> print ih[0]       # prints 0x00 because this location is blank

Summarizing the data chunks

One of the more useful properties of HEX files is that they can specify data in discontinuous segments. There are two main methods to summarize which data addresses are occupied:

>>> ih.addresses()
>>> ih.segments()

The first will return a list of occupied data addresses in sorted order. The second will return a list of 2-tuples objects, in sorted order, representing start and stop addresses of contiguous segment chunks of occupied data. Those 2-tuples are suitable to be used as start and stop arguments of standard range function.