Multichannel Serial Interfaces
9-36
Then, to release the interrupt signal and reset the corresponding status bits:
-
DSP_WRITE(1) =
J
STATUS_REG(1) for FERR_INT release
J
STATUS_REG(2) for RX_INT release
J
STATUS_REG(4) for TX_INT release
9.5.1.5
DMA Channel Operation
Both transmit and receive operations can be supported by DMA. DMA support
is enabled by control bits in the MAIN_PARAMETERS_REG:
-
MAIN_PARAMETERS_REG(15:14) = DMA_ENABLE(1:0)
J
TX_DMA_REQ enabled when DMA_ENABLE(0) = 1
J
TX_DMA_REQ disabled when DMA_ENABLE(0) = 0
J
RX_DMA_REQ enabled when DMA_ENABLE(1) = 1
J
RX_DMA_REQ disabled when DMA_ENABLE(1) = 0
Transmit DMA Transfers
A new transmit DMA transfer is initiated during the transmission of the last
channel of a frame, at which time all data in the transmit registers (TX_REGs)
has been moved to shift registers; the TX_REGs are now ready to be rewritten.
If N channels are used, the DMA controller successively accesses all consecu-
tive registers between TX_REG(0) and TX_REG(N-1). If some channels
between TX_REG(0) and TX_REG(N-1) are not used, the DMA controller
writes dummy values when addressing these unused registers (see
Figure 9–14).
Figure 9–14. Transmit DMA Transfers
MCSI
dma add
Val0
Ad0
Valn
dum
Adn
TI peripheral bus
ad
n-1
Ad1
dum
Value 0
Empty N
Empty n+1
Value n
Dummy n-1
Dummy 1
Value 0
Empty N
Empty n+1
Value n
Empty n-1
Empty 1
MCSI Tx
registers
MCSI Tx
shift
registers
Serial output
Value 0 Value n