Renesas SH7781 - Manual (Page 1319)

25. Audio Codec Interface (HAC)
Rev.1.00 Jan. 10, 2008 Page 1289 of 1658
REJ09B0261-0100
25.5.3 DMA
The HAC supports DMA transfer for slots 3 and 4 of both the RX and TX frames. Specify the slot
data size for DMA transfer, 16 or 20 bits, with the DMARX16 and DMATX16 bits in HACACR.
When the data size is 20 bits, transfer of data slots 3 and 4 requires two local bus access cycles.
Since each of the receiver and transmitter has its DMA request, the stereo mode generates a DMA
request for slots 3 and 4 separately. The mono mode generates a DMA request for just one slot.
When the data size is 16 bits, data from slots 3 and 4 are packed into a single 32-bit quantity (left
data and right data are in PCML), which requires only one local bus access cycle.
It may be necessary to halt a DMA transfer before the end count is reached, depending on system
applications. If so, clear the corresponding DMA bit in HACACR to 0 (DMA disabled). To
resume a DMA transfer, reprogram the DMAC and then set the corresponding DMA bit to 1
(DMA enabled).
25.5.4 Interrupts
Interrupts can be used for flag events from the receiver and transmitter. Make the setting for each
interrupt in the corresponding interrupt enable register. Interrupts include a request to the CPU to
read/write slot data, overrun and underrun. To get the interrupt source, read the status register.
Writing 0 to the bit will clear the corresponding interrupt.