Question 1

What is an ISO 8583 bitmap?

Accepted Answer

The bitmap in ISO 8583 is a field that indicates which data elements are present in the message. Each bit position corresponds to a data field number. If a bit is set to 1, that field is included in the message.

Question 2

What is the difference between primary and secondary bitmaps?

Accepted Answer

The primary bitmap (64 bits) covers fields 1-64. If bit 1 is set, a secondary bitmap follows, covering fields 65-128. This allows ISO 8583 messages to contain up to 128 data fields.

Question 3

How is the bitmap encoded?

Accepted Answer

The bitmap is typically encoded as hexadecimal. The primary bitmap is 16 hex characters (64 bits). If the first bit is set (bit 1), an additional 16 hex characters follow for the secondary bitmap.

Question 4

How do I know which fields are present?

Accepted Answer

Enter the hex bitmap in the tool, and it will display all bit positions (1-64 or 1-128). Checked boxes indicate fields present in the message. You can also build a bitmap by selecting the fields you need.

ISO8583 Bitmap

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ISO8583 Bitmap FAQ