RM0082
LS_Synchronous serial peripheral (SSP)
Doc ID 018672 Rev 1
273/844
parallel to serial conversion, then output the serial data stream and frame control signal
through the slave SSPTXD pin. The slave receive logic performs serial to parallel conversion
on the incoming SSPRXD data stream, extracting and storing values into its receive FIFO,
for subsequent reading through the APB interface.
13.4.7 Interrupt
generation
logic
The PrimeCell SSP generates four individual maskable, active HIGH interrupts.
A combined interrupt output is also generated as an OR function of the individual interrupt
requests.
You can use the single combined interrupt with a system interrupt controller that provides
another level of masking on a per-peripheral basis. This allows use of modular device
drivers that always know where to find the interrupt source control register bits.
The individual interrupt requests could also be used with a system interrupt controller that
provides masking for the outputs of each peripheral. In this way, a global interrupt controller
service routine would be able to read the entire set of sources from one wide register in the
system interrupt controller. This is attractive where the time to read from the peripheral
registers is significant compared to the CPU clock speed in a real-time system.
The peripheral supports both the above methods.
The transmit and receive dynamic data-flow interrupts, TXINTR and RXINTR, are separated
from the status interrupts so that data can be read or written in response to the FIFO trigger
levels.
13.4.8 DMA
interface
This block manages the DMA interface. It can work in single transfer mode or in burst
transfer mode.
Refer to the
to have more detail on this Interface.
13.4.9
Synchronizing registers and logic
The SSP supports both asynchronous and synchronous operation of the clocks, PCLK and
SSPCLK. Synchronization registers and hand shaking logic have been implemented, and
are active at all times. This has a minimal impact on performance or area. Synchronization
of control signals is performed on both directions of data flow, which is from the PCLK to the
SSPCLK domain and from the SSPCLK to the PCLK domain.
13.5 SSP
operation
In the following sections are described the operation of the SSP block.
13.5.1 Configuring
the
SSP
Following reset, the SSP logic is disabled and must be configured when in this state.