RM0082
LS_Synchronous serial peripheral (SSP)
Doc ID 018672 Rev 1
285/844
Provision of the individual outputs as well as a combined interrupt output, allows use of
either a global interrupt service routine, or modular device drivers to handle interrupts.
The transmit and receive dynamic dataflow interrupts SSPTXINTR and SSPRXINTR have
been separated from the status interrupts, so that data can be read or written in response to
just the FIFO trigger levels.
The status of the individual interrupt sources can be read from SSPRIS and SSPMIS
registers.
13.7.1 SSPRXINTR
The receive interrupt is asserted when there is four or more valid entries in the receive FIFO.
13.7.2 SSPTXINTR
The transmit interrupt is asserted when there are four or less valid entries in the transmit
FIFO. The transmitter interrupt SSPTXINTR is not qualified with the SSP enable signal,
which allows operation in one of two ways. Data can be written to the transmit FIFO prior to
enabling the PrimeCell SSP and the interrupts. Alternatively, the SSP and interrupts can be
enabled so that data can be written to the transmit FIFO by an interrupt service routine.
13.7.3 SSPRORINTR
The receive overrun interrupt SSPORINTR is asserted when the FIFO is already full and an
additional data frame is received, causing an overrun of the FIFO. Data is over-written in the
receive shift register, but not the FIFO.
13.7.4 SSPRTINTR
The receive timeout interrupt is asserted when the receive FIFO is not empty and the SSP
has remained idle for a fixed 32 bit period. This mechanism ensures that the user is aware
that data is still present in the receive FIFO and requires servicing. This interrupt is
deasserted if the receive FIFO becomes empty by subsequent reads, or if new data is
received on SSPRXD. It can also be cleared by writing to the RTIC bit in the SSPICR
register.
13.7.5 SSPINTR
The interrupts are also combined into a single output SSPINTR, that is an OR function of
the individual masked sources. You can connect this output to the system interrupt controller
to provide another level of masking on an individual per-peripheral basis. The combined
SSP interrupt is asserted if any of the four individual interrupts above are asserted and
enabled.