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215
Serial Controller Module
Little Endian mode configuration. Transmits first the least significant bytes
in the word written to the FIFO. For example, the long word
0x11223344
results in the character
0x44 being transmitted first and 0x11 being
transmitted last.
Processor interrupts vs. DMA
The transmit FIFO can be filled using processor interrupts or DMA.
When using processor interrupts, the processor can write one long word (4
bytes) of data to the transmit FIFO when the TRDY bit in Serial Channel
Status Register A is active high. If the THALF bit in Serial Channel Status
Register A is active high, the processor can write four long words (16 bytes)
of data to the transmit FIFO. To facilitate an interrupt when either the
TRDY or THALF status bit is active, the processor can set one or both of the
corresponding interrupt enables — ETXRDY, ETXHALF — in Serial Channel
Control Register A. The appropriate interrupt enable bit — SER 1 TX or
SER 2 TX — in the GEN module Interrupt Enable register must also be set.
When using the DMA controller, the processor must interface with the DMA
channel registers and the DMA buffer descriptor block attached to DMA
channels 8 and 10. To facilitate the use of transmit DMA, the ETXDMA bit in
Serial Channel Control Register A must be set active high and the serial
transmitter interrupts should be disabled.
Receive FIFO interface
The receive FIFO presents up to four bytes of data at a time to the processor
interface. The number of valid bytes found in the next read of the FIFO is defined by
the information found in the RXFDB field in Serial Channel Status Register A.
The Endian rules described for the transmit FIFO also apply for the receive FIFO; see
"Operating in Endian modes" on page 214.
When reading from the receive FIFO, the processor must perform a long word read
operation. Each time a read cycle is performed, the receive FIFO goes to the next
long word entry. The processor cannot read individual bytes from the same FIFO long
word entry.
Processor interrupts vs. DMA
The receive FIFO can be emptied using processor interrupts or DMA.