9F66 Terminal Transaction Qualifiers (TTQ)

The Terminal Transaction Qualifiers are four bytes a contactless reader sends to the card in the GET PROCESSING OPTIONS command, because the card asks for them in its PDOL. They tell the card what the reader supports and what it requires for this transaction. The TTQ is central to Visa's Kernel 3 and is also used by several other kernels built on the same model.

Main bits

• Byte 1: b8 magnetic stripe mode supported, b6 EMV mode supported, b5 EMV contact chip supported, b4 offline-only reader, b3 online PIN supported, b2 signature supported, b1 offline data authentication for online authorisations supported.
• Byte 2: b8 online cryptogram required, b7 CVM required, b6 offline PIN supported (contact chip).
• Byte 3: b8 issuer update processing supported, b7 consumer device CVM supported.
• Byte 4: reserved.

How it is used

The card combines the TTQ with its own settings to decide the outcome and the CVM. For example, if the reader sets "CVM required" because the amount is above the CVM limit, the card answers with the CVM it wants in its Card Transaction Qualifiers (9F6C). If the reader sets "online cryptogram required", the card returns an ARQC. Bits in bytes 2 and 3 can change from one transaction to the next, because the reader sets them after comparing the amount with its limits.

Example

9F66 04 36 00 40 00: EMV mode and contact chip supported, online PIN and signature supported, consumer device CVM supported, with no online cryptogram or CVM required for this transaction.

Common mistakes

• Sending a fixed TTQ for every transaction instead of setting "CVM required" and "online cryptogram required" from the amount and limits.
• Declaring consumer device CVM unsupported, which makes phone payments above the CVM limit fail or fall back.
• Decoding a TTQ with a different kernel's definitions. Check which kernel the card selected.