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13-32 Intel® PXA255 Processor Developer’s Manual
AC’97 Controller Unit
13.8.3.17 Accessing CODEC Registers
Each CODEC has up to sixty-four 16-bit registers that are addressable internal to the CODEC at
half-word boundaries (16-bit boundaries). Because the processor only supports internal register
accesses at word boundaries (32-bit boundaries), software must select the one of the following
formulas to translate a 7-bit CODEC address into a 32-bit processor address:
• Processor physical address for a Primary Audio CODEC
= 0x4050-0200 + Shift_Left_Once(Internal 7-bit CODEC Register Address)
• Processor physical address for a Secondary Audio CODEC
= 0x4050-0300 + Shift_Left_Once(Internal 7-bit CODEC Register Address)
• Processor physical address for a Primary Modem CODEC
= 0x4050-0400 + Shift_Left_Once(Internal 7-bit CODEC Register Address)
• Processor physical address for a Secondary Modem CODEC
= 0x4050-0500 + Shift_Left_Once(Internal 7-bit CODEC Register Address)
In the equations, Shift_Left_Once() shifts the 7-bit CODEC address left by one bit and shifts a 0 to
the LSB. The address translations are shown in Table 13-23.
Figure 13-11. Modem Transmit and Receive Operation
TxEntry0
TxEntry1
TxEntry2
TxEntry3
TxEntry15
15 0
RxEntry0
RxEntry1
RxEntry2
RxEntry3
RxEntry15
15 0
MODR Register
31 0
Processor/DMA Processor DMA
Modem Transmit FIFO Modem Receive FIFO
1516
0x0000
Write Read
Transmit
data
Receive
Data