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NEO 2 Interface Developer’s Guide
Copyright © 2019, International Technologies & Systems Corporation. All rights reserved.
56
3.3.1.3.
NACK Frame
If the terminal fails to receive the card payload data, it can send a NACK frame and request the
ViVOpay reader to resend the card payload data. To ensure that the reader resends the card
payload data, the NACK frame must be received by the reader within 500ms after it sends the
original card payload. If the reader receives the NACK frame within this time period, it resends
the card payload data to the terminal. If the reader receives the NACK Frame after 500ms of
sending the original card payload, or if a new card has been detected, the reader ignores the
NACK frame and does not resend the payload data. Each payload data is only resent one time.
The NACK frame is a 1-Byte code with value of 0x55.
Byte 0
Frame Type =0x55h
Example 1
: ViVOpay receives NACK frame from terminal within 500ms after sending the
original payload data, ViVOpay resends the card payload data.
Terminal
ViVOpay Reader
Original Payload
◄
---------------------------------------------------------------------
| Time: 0
|
NACK sent at 400ms (within 500ms)
|
--------------------------------------------------------------------
►
| Time: 400ms
|
Resend Payload
|
◄
---------------------------------------------------------------------
|
▼
Original Payload:
Payload, Card Read Successfully, Application Type Master Card, Both Track 1 and Track 2
Present
[01][00][01]%B5325350000623567^840SMITH/JOHN^05085011492563892473?
;5325350000623567=05081019492993892483? <CRC1><CRC2>
Resent payload:
Payload, Card Read Successfully, Application Type Master Card, Both Track 1 and Track 2
Present
[01][00][01]%B5325350000623567^840SMITH/JOHN^05085011492563892473?
;5325350000623567=05081019492993892483? <CRC1><CRC2>