K60P100M100SF2RM Datasheet, PDF (1733/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 53 Integrated interchip sound (I2S)
While using AC97 in two-channel mode (CR[TCHEN] = 1), it is recommended that the
received tag is not stored in the Rx FIFO (ACNT[TIF] = 0). If you need to update the
ATAG register and also issue a RD/WR command (in a single frame), it is recommended
that the ATAG register is updated prior to issuing a RD/WR command.
53.4.1.5.1 AC97 fixed mode (ACNT[FV] = 0)
In fixed mode, I²S transmits in accordance with the AC97 frame rate divider bits
(ACNT[FRDIV) that decide the number of frames for which the I²S should be idle, after
operating for one frame. The following shows the slot assignments in a valid transmit
frame:.
• Slot 0: The tag value (written by the user program)
• Slot 1: If RD/WR command, command address
• Slot 2: If WR command, command data
• Slot 3–12: Transmit FIFO data, depending on the valid slots indicated by the TAG
value
While receiving, bit 15 of the tag slot is checked to see if the codec is ready. If this bit is
set, the frame is received. The received tag provides the information about slots
containing valid data. If the corresponding tag bit is valid, the command address (slot #1)
and command data (slot #2) values are stored in the corresponding registers. The received
data (slot #3–12) is then stored in the receive FIFO (for valid slots).
53.4.1.5.2 AC97 variable mode (ACNT[FV] = 1)
In variable mode, the transmit slots that should contain data in the current frame are
determined by the SLOTREQ bits received in the previous frame. While receiving, if the
codec is ready, the frame is received and the SLOTREQ bits are stored for scheduling
transmission in the next frame.
The ACCST, ACCEN and ACCDIS registers helps determine which transmit slots are
active. This information is used to ensure that I²S does not transmit data for powered-
down/inactive channels.
53.4.2 I²S clocking
The I²S uses the following clocks:
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
1733