NXP Semiconductors K32 L2A Series, Reference Manual, Page: 523 / 1379

NOTE
Setting any other value for CRC_IN_FLIP, CRC_OUT_FLIP
and INV_CRC_VAL will cause CRC value to be formatted
accordingly; however the CRC will not be compliant to the
standard CRC used in Smart Cards.
The CRC value can be reset/initialized in multiple ways. Clearing the CRC_EN bit in the
CTRL register will reset the CRC value. At the end of a transmission (either after the
CRC characters are transmitted, or after the last character in the transmit FIFO is sent
when XMT_CRC_LRC is clear), the CRC value is automatically reset by the EMV SIM
hardware. Finally, when setting the XMT_EN bit, the EMV SIM hardware resets the
CRC value.
Summary of configuration needed to use CRC block:
• Use CRC_IN_FLIP, CRC_OUT_FLIP and INV_CRC_VAL bits in CTRL register to
select the desired CRC method (CCITT or normal)
• Use the CRC_EN bit in CTRL register to enable the CRC block
• Use the XMT_CRC_LRC bit to enable the transmission of the CRC Characters after
the last character in the Transmit FIFO is sent.
21.6.6 Message Handling
The EMV SIM module has FIFOs on both transmit and receive side for handling all
message bytes.
21.6.6.1 Transmit FIFO
A 4-byte deep FIFO is implemented in the transmitter. The transmit FIFO can be written
into by the software but reads to this FIFO will return zeros. To take care of clock
synchronization, each write access will have wait states inserted by the module but this is
transparent to the software. The Tx FIFO can be written to while the transmitter is
enabled, however, the transmitter does not start transmitting while the FIFO is empty. A
write to the Tx FIFO will initiate the transmit operation. Software can store more bytes
into the Tx FIFO until the programmed threshold is reached. Software can enable DMA
operation by setting TX_DMA_EN = 1 in the CTRL register. On setting this bit, a DMA
request will be asserted and remain asserted till the number of bytes in FIFO reached the
programmed threshold value (TDT[3:0] in the TX_THD register).
Chapter 21 Smart Card Interface Module (EMV SIM)
K32 L2A Reference Manual, Rev. 2, 01/2020
NXP Semiconductors 523