Rainbow Electronics AT91CAP9S250A - Manual (Page 622)

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6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
37.6.1.1 Slot Description
Tag Slot
The tag slot, or slot 0, is a 16-bit wide slot that always goes at the beginning of an outgoing or
incoming frame. Within tag slot, the first bit is a global bit that flags the entire frame validity.
The next 12 bit positions sampled by the AC’97 Controller indicate which of the corresponding
12 time slots contain valid data. The slot’s last two bits (combined) called Codec ID, are used
to distinguish primary and secondary codec.
The 16-bit wide tag slot of the output frame is automatically generated by the AC‘97 Controller
according to the transmit request of each channel and to the SLOTREQ from the previous
input frame, sent by the AC‘97 Codec, in Variable Sample Rate mode.
Codec Slot 1
The command/status slot is a 20-bit wide slot used to control features, and monitors status for
AC‘97 Codec functions.
The control interface architecture supports up to sixty-four 16-bit wide read/write registers.
Only the even registers are currently defined and addressed.
Slot 1’s bitmap is the following:
• Bit 19 is for read/write command, 1= read, 0 = write.
• Bits [18:12] are for control register index.
• Bits [11:0] are reserved.
Codec Slot 2
Slot 2 is a 20-bit wide slot used to carry 16-bit wide AC97 Codec control register data. If the
current command port operation is a read, the entire slot time is stuffed with zeros. Its bitmap
is the following:
• Bits [19:4] are the control register data
• Bits [3:0] are reserved and stuffed with zeros.
Data Slots [3:12]
Slots [3:12] are 20-bit wide data slots, they usually carry audio PCM or/and modem I/O data.
10 Modem Line 2 ADC
11 Modem Handset Input ADC
12 Modem IO Status
Table 37-3. AC-link Input Slots Transmitted from the AC’97C Controller
Slot # Pin Description