NXP Semiconductors K32 L2A Series, Reference Manual, Page: 518 / 1379

21.6.3.4 NACK Detection
During transmission of message bytes, the receiver automatically checks for NACKs sent
by the Smart Card. The software does not need to enable receiver for this. The NACK is
detected by sampling the IO line at 11 ETUs after the falling edge of the START bit.
Once a NACK is detected, the transmitter is signaled and the transmitter will retransmit
the current byte after two ETU time (as per ISO 7816 specification).
21.6.3.5 Using EMV SIM Receiver with "T=1" Smart Cards
The EMV SIM module provides hardware support for “T=1” type Smart Cards. These
type of cards present several requirements above and beyond the standard “T=0” cards.
The features provided to meet the requirements that pertain to the EMV SIM receiver are
as follows:
• 11 ETU Characters
• “T=1” cards can transmit with character lengths of 11 ETUs (that is, one STOP
bit). The EMV SIM module provides the RCVR11 bit in the CTRL register in
order to configure the receiver state machine to accept 11 ETU characters.
• Character Wait Time Counter
• The character waiting time (CWT) is defined as the time between the start bits of
two consecutive characters received from the Smart Card. The value of CWT
can range from 12 ETU to 32779 ETU. The EMV SIM module provides a 16-bit
counter with programmable comparator clocked at the ETU bit rate to identify
when the CWT has been exceeded by the Smart Card.
• Block Wait Time
• The block waiting time (BWT) is defined as the maximum time between the start
bits of the last character of a transmitted block and the first character of the next
received block. The block wait time must not exceed a value that is
programmable. The EMV SIM module provides a 32-bit Block Wait Timer that
can be used to identify when the BWT has been violated.
• Block Guard Time
• The block guard time (BGT) is defined as the minimum delay between the start
bits of the last character of a transmitted block and the first character of the next
received block. The block guard must be greater than a value that is
programmable. The EMV SIM module provides a 16-bit Block Guard Timer that
can be used to identify when the BGT has been violated.
• Error Detection Code
• “T=1” cards can specify LRC or CRC error detection codes to be used. The
EMV SIM module provides hardware support for both the LRC and CRC
operations.
Functional Description
K32 L2A Reference Manual, Rev. 2, 01/2020
518 NXP Semiconductors