Receive Fifo; Interrupt Generation Logic; Dma Interface - Wiznet W7500 Reference Manual

Receive FIFO

The common receive FIFO is a 16-bit wide, 8-locations deep, first-in, first-out memory buffer.
Received data from the serial interface are stored in the buffer until it is read out by the CPU
across the AMBA APB interface.
When configured as a master or slave, serial data received through the SSPRXD pin is registered
prior to parallel loading into the attached slave or master receive FIFO.

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.
Users can use the single combined interrupt with a system interrupt controller that provides
another level of masking on a per-peripheral basis. This enables use of modular device drivers
that always know where to find the interrupt source control register bits.
Users can also use the individual interrupt requests with a system interrupt controller that
provides masking for the outputs of each peripheral. In this way, a global interrupt controller
service routine can read the entire set of sources from one wide register in the system
interrupt controller. This is attractive when 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 methods above.
The transmit and receive dynamic data-flow interrupts, SSPTXINTR and SSPRXINTR, are
separated from the status interrupts so that data can be read or written in response to the
FIFO trigger levels.

DMA interface

The PrimeCell SSP provides an interface to connect to the DMA controller. The PrimeCell SSP
DMA control register, SSPDMACR controls the DMA operation of the PrimeCell SSP.
Receive – The DMA interface includes the following signals for receive:
- SSPRXDMASREQ
Single-character DMA transfer request asserted by the SSP. This signal is

asserted when the receive FIFO contains at least one character.
- SSPRXDMABREQ
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