Toshiba TMPR4925, Manual

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Chapter 14 AC-link Controller
14-10
14.3.6.2 DMA Channel Mapping
ACLC uses four DMA request channels. These DMA channels are allocated to four out of
seven data-streams, or slots, on the AC-link frame, according to ACLC DMA Channel Selection
Register (ACDMASEL) setting as shown in Table 14.3.1. The pin configuration register allocates
these DMA channels of ACLC to the DMAC (DMA controller) channels according to DMA
Request Control Register (DRQCTR)’s DMA Request Selection (DMAREQ0-3) bits as described
in section 5.2.8.
Table 14.3.1 DMA Channel Mapping Modes
ACDMASEL
AC-link Slot Number 0 1 2 3
PCM L&R out (3&4) ACLC ch0 ACLC ch0 ACLC ch0 ACLC ch0
Surround L&R out (7&8) ACLC ch1 ACLC ch1 ACLC ch1
Center out (6) ACLC ch2
LFE out (9) ACLC ch3 ACLC ch3
PCM L&R in (3&4) or Mic in (6) ACLC ch1 ACLC ch2
Modem Line1 out (5) ACLC ch2 ACLC ch2
Modem Line 1 in (5) ACLC ch3 ACLC ch3
14.3.6.3 Sample-data Format
ACLC transmits/receives 16 bits per sample for each data slot shown in Table 14.3.1. The data
resides on the first 16 bits of the 20 bits assigned to each slot on AC-link. Each sample-data
register allows access by word (32-bit) unit only. Therefore the DMA count must be a multiple of
word. Note that the transmit-data DMA count also must be the FIFO depth (refer to Table 14.3.8)
or more for a reason described later.
For audio PCM front and surround streams, every data-word is loaded with a couple of left and
right samples. For audio MIC stream, valid data is loaded in the same field as the left sample
while the other field is filled with ‘0’. For audio center, LFE, and modem line 1 streams, two
consecutive samples are packed into every word.
The data format at the sample-data register is arranged so that the data format on the DMA
buffer follows the rules below.
•
Each sample data is put in the byte order in which the CPU operates (big- or little-endian).
•
Samples are put in the time-sequential order at increasing addresses on memory.
•
For a DMA channel which couples left and right samples, each left sample precedes the
corresponding right sample.
Refer to the sections 14.4.16 and later for the register format.