srec_dec_binary(5)

NAME
srec_dec_binary - DEC Binary (XXDP) file format

DESCRIPTION
The DEC Binary (XXDP) format was used on the PDP 11 series machines. This is a binary format, and is not readable or editable with a text editor. The file consists of records of the form
type | length | address | ...data... | checksum
The field are defined as follows:

type
    Two byte little-endian value. Must always be 1.

length
    Two byte little-endian value. This is the number of bytes in the data, plus six.

address
    Two byte little-endian value. This is the load address of the data.

data
    The data is simple raw bytes. There are (length-6) of them.

checksum
    The checcksum is a single byte. It is the negative of the simple summ of all the header and data bytes.

If the record length is exactly 6 (i.e. no data), this is the execution start address record, indicating the transfer address.

In addition there may be NUL padding characters between records. It is common for records to be padded so that they start on even byte boundaries. In the days of paper tape, it was common for the file to have many leading NULs, to generate blank leader on the tape.

  Size Multiplier
In general, raw binary data will expand in sized by approximately 1.03 times when represented with this format.