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Intel® PXA255 Processor Developer’s Manual 14-9
Inter-Integrated-Circuit Sound (I2S) Controller
14.6.1.1 Special purpose FIFO Read/Write function
As shown in Table 14-4, EFWR and STRF can be programmed for special purpose FIFO accesses.
Under normal operating conditions, the processor or the DMA controller can only write to the
Transmit FIFO and only read the Receive FIFO. Programming these bits allows the processor or
the DMA controller to read and write both FIFOs.
Table 14-3. SACR0 Bit Definitions
Physical Address
0x4040_0000
Serial Audio Controller Global
Control Register
I
2
S Controller
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
reserved RFTH TFTH
reserved
STRF
EFWR
RST
BCKD
reserved
ENB
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 1 1 0 0 0 0 0 0 0 0
Bits Name Description
31:16 — reserved
15:12 RFTH
Receive FIFO interrupt or DMA threshold. Set to value 0 – 15. This value must be set to the
threshold value minus 1.
Receive DMA Request asserted whenever the Receive FIFO has >= (RFTH+1) entries.
11:8 TFTH
Transmit FIFO interrupt or DMA threshold. Set to value 0 – 15. This value must be set to
the threshold value minus 1.
Transmit DMA Request asserted whenever the Transmit FIFO has < (TFTH+1) entries.
7:6 — reserved
5STRF
Select Transmit or Receive FIFO for EFWR based special purpose function:
0 = Transmit FIFO is selected
1 = Receive FIFO is selected
See Table 14-4 for details.
4EFWR
This bit enables a special purpose FIFO Write/Read function:
0 = Special purpose FIFO Write/Read Function is disabled
1 = Special purpose FIFO Write/Read Function is enabled
See Table 14-4 for details.
3RST
Resets FIFOs logic and all registers, except this register (SACR0):
0 = Not reset
1 = Reset is active to other registers
2BCKD
This bit specifies input/output direction of BITCLK:
0 = Input. BITCLK driven by an external source.
1 = Output. BITCLK generated internally and driven out to the CODEC.
1 — reserved
0ENB
Enable I
2
S function:
0 = I2SLINK is disabled
1 = I2SLINK is enabled