NXP Semiconductors K22F series, Reference Manual, Page: 1179 / 1407

TX FIFO Base - Base address of TX FIFO
TXCTR - TX FIFO Counter
TXNXTPTR - Transmit Next Pointer
TX FIFO Depth - Transmit FIFO depth, implementation specific
45.5.6.2 Address Calculation for the First-in Entry and Last-in Entry
in the RX FIFO
The memory address of the first-in entry in the RX FIFO is computed by the following
equation:
The memory address of the last-in entry in the RX FIFO is computed by the following
equation:
RX FIFO Base - Base address of RX FIFO
RXCTR - RX FIFO counter
POPNXTPTR - Pop Next Pointer
RX FIFO Depth - Receive FIFO depth, implementation specific
Chapter 45 Serial Peripheral Interface (SPI)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 1179