ISO 8583 · Data fields

Field 46Additional Data · ISO

pyiso8583 starter profilesIndependent explanation

What this field describes

The starter profile provides a variable length container labelled Additional Data ISO.

The label is not a schema for its contents. This reference does not reproduce the standard’s additional data definitions.

Compare the two profiles

Container settings from the pinned pyiso8583 source.
Setting	`default`	`default_ascii`
Value encoding	ASCII	ASCII
Length limit	Up to 999 bytes	Up to 999 bytes
Prefix	3 ASCII bytes	3 ASCII bytes

Length limits describe encoded values. They exclude any length prefix. The profiles can be customized; these settings do not establish the required fields or accepted values for a live connection.

Read the field boundary

Length prefix3 bytesASCII length

Field 46≤ 999 bytesASCII value

Read the 3 prefix bytes first, then read that many value bytes. Reject a length that exceeds 999 or the bytes remaining in the message.

Find it in the bitmap

Bitmap: Primary
Position: 46
Byte: 6
Bit in byte: 6

Positions start at one. Bits are counted from the most significant bit of each bitmap byte. This calculation locates the field’s presence indicator, not its value.