
1036
6437E–ATARM–23-Apr-13
SAM9M11
43.7.2
Slot Description
43.7.2.1
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 AC97 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 dis-
tinguish primary and secondary codec.
The 16-bit wide tag slot of the output frame is automatically generated by the AC97 Controller
according to the transmit request of each channel and to the SLOTREQ from the previous input
frame, sent by the AC97 Codec, in Variable Sample Rate mode.
43.7.2.2
Codec Slot 1
The command/status slot is a 20-bit wide slot used to control features, and monitors status for
AC97 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.
43.7.2.3
Codec Slot 2
Slot 2 is a 20-bit wide slot used to carry 16-bit wide AC97 Codec control register data. If the cur-
rent 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.
43.7.2.4
Data Slots [3:12]
Slots [3:12] are 20-bit wide data slots, they usually carry audio PCM and/or modem I/O data.