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CSU Builder

Build and decode EMV Card Status Update commands — per EMVCo Book 3 CCD Table 11

Byte 1 Authentication & PIN Try Counter 0x00
b8 Proprietary Authentication Data Included
b4-b1 PIN Try Counter (0–15)
Byte 2 Issuer Actions & Counter Updates 0x00
b8 Issuer Approves Online Transaction
b7 Card Block
b6 Application Block
b5 Update PIN Try Counter
b4 Set Go Online on Next Transaction
b3 CSU Created by Proxy for Issuer
b2-b1 Update Counters
Byte 3 RFU (Reserved for Future Use) 0x00
b8-b1 All bits reserved — always 00
Byte 4 Issuer-Discretionary 0x00
b8-b1 Issuer-Discretionary Data
Generated CSU (4 bytes)
00000000
Total Bytes 4
Specification EMVCo Book 3 CCD
Active Flags 0

Enter an 8-character hex string (4 bytes). Spaces are OK.

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📖 About This Tool

What is the CSU Builder?

The CSU Builder creates Card Status Update (CSU) byte values used in EMV issuer scripts. CSU controls post-authorization actions like blocking/unblocking the application or updating PIN try counters.

🛠️ How to Use
  1. Select the desired card actions.
  2. Configure PIN try counter and issuer discretionary bits.
  3. Click Build to generate the CSU hex value.
❓ FAQ

What is CSU used for?

CSU (Card Status Update) is part of the Issuer Authentication Data in the ARPC response. It instructs the card to perform actions like resetting the PIN try counter, blocking the application, or updating internal counters.