NXP Semiconductors K22F series, Reference Manual, Page: 1366 / 1407

If the SAI transmitter or receiver is using an externally generated bit clock in
asynchronous mode and that bit clock is generated by an SAI that is disabled in stop
mode, then the transmitter or receiver should be disabled by software before entering stop
mode. This issue does not apply when the transmitter or receiver is in a synchronous
mode because all synchronous SAIs are enabled and disabled simultaneously.
49.4.1.3 Bus clock
The bus clock is used by the control and configuration registers and to generate
synchronous interrupts and DMA requests.
NOTE
Although there is no specific minimum bus clock frequency
specified, the bus clock frequency must be fast enough (relative
to the bit clock frequency) to ensure that the FIFOs can be
serviced, without generating either a transmitter FIFO underrun
or receiver FIFO overflow condition.
49.4.2 SAI resets
The SAI is asynchronously reset on system reset. The SAI has a software reset and a
FIFO reset.
49.4.2.1 Software reset
The SAI transmitter includes a software reset that resets all transmitter internal logic,
including the bit clock generation, status flags, and FIFO pointers. It does not reset the
configuration registers. The software reset remains asserted until cleared by software.
The SAI receiver includes a software reset that resets all receiver internal logic, including
the bit clock generation, status flags and FIFO pointers. It does not reset the configuration
registers. The software reset remains asserted until cleared by software.
49.4.2.2 FIFO reset
The SAI transmitter includes a FIFO reset that synchronizes the FIFO write pointer to the
same value as the FIFO read pointer. This empties the FIFO contents and is to be used
after TCSR[FEF] is set, and before the FIFO is re-initialized and TCSR[FEF] is cleared.
The FIFO reset is asserted for one cycle only.
Functional description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
1366 NXP Semiconductors