ISO 8583 · Data fields

Field 55ICC data

pyiso8583 starter profilesIndependent explanation

What this field describes

ICC data uses a variable length container. The default profile carries binary bytes, while default_ascii carries an ASCII representation.

The container is not an EMV tag dictionary. Interpret any tags using the relevant chip data specification and encoding rules.

Compare the two profiles

Container settings from the pinned pyiso8583 source.
Setting	`default`	`default_ascii`
Value encoding	Binary	ASCII
Length limit	Up to 255 bytes	Up to 510 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 55≤ 510 bytesASCII value

Read the 3 prefix bytes first, then read that many value bytes. Reject a length that exceeds 510 or the bytes remaining in the message.

Find it in the bitmap

Bitmap: Primary
Position: 55
Byte: 7
Bit in byte: 7

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.