Multichannel Serial Interfaces
9-37
DSP Public Peripherals
Receive DMA Transfers
A receive DMA transfer is initiated after the reception of the last channel of a
frame, at which time all receive registers RX_REG have been updated and are
ready to be read. If N channels are used, the DMA controller successively
accesses all consecutive registers between RX_REG(0) and RX_REG(N-1).
If some channels between RX_REG(0) and RX_REG(N-1) are not used, the
DMA controller reads dummy values when addressing these unused registers
(see Figure 9–15).
Figure 9–15. Receive DMA Transfers
MCSI
dma add
dma data
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 Rx
registers
MCSI Rx
shift
registers
Serial input
Value 0 Value n
A multichannel application cannot use DMA for some channels and interrupt
servicing for others. RX/TX interrupts are not generated when DMA RX/TX
transfers are enabled.