Cirrus Logic EP93xx - Manual (Page 695)

DS785UM1 22-7
Copyright 2007 Cirrus Logic
AC’97 Controller
EP93xx User’s Guide
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Address:
AC97DR1 - 0x8088_0000 - Read/Write
AC97DR2 - 0x8088_0020 - Read/Write
AC97DR3 - 0x8088_0040 - Read/Write
AC97DR4 - 0x8088_0060 - Read/Write
Definition:
The AC97DR registers are read / write data registers that are normally 20 bits
wide. In 16-bit compact mode, all 32 available bits are used. This register is
zero at reset.
Bit Descriptions:
RSVD: Reserved. Unknown During Read.
DATA: Write - Transmit FIFO: The AC97TXCR register qualifies
the data within the TX FIFO.
Read - Receive FIFO: The AC97RXCR register qualifies
the data within the FIFO.
For words to be transmitted:
• If the FIFOs are enabled, data written to this location is pushed onto the transmit FIFO.
• If the FIFOs are not enabled, data is stored in the transmitter holding register (the bottom
word of the transmit FIFO).
For received words:
• If the FIFOs are enabled, the data received is pushed onto the receive FIFO.
• If the FIFOs are not enabled, the data received is stored in the receiving holding register
(the bottom word of the receive FIFO).
The receive FIFO is 21 bits wide. The 21
st
bit, the receive overrun error status, can only be
read via the AC97ISR registers. The receive overrun error status bit is transferred down to
the FIFO buffer along with the overrun data value.
AC97RXCRx
Address:
AC97RXCR1 - 0x8088_0004 - Read/Write
AC97RXCR2 - 0x8088_0024 - Read/Write
AC97RXCR3 - 0x8088_0044 - Read/Write
AC97RXCR4 - 0x8088_0064 - Read/Write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
RSVD TOC FDIS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
CM RSIZE RX12 RX11 RX10 RX9 RX8 RX7 RX6 RX5 RX4 RX3 RX2 RX1 REN