876784 Intel, 876784 Datasheet - Page 237

• Manufacturer Part Number: 876784
• Manufacturer: Intel

Specifications of 876784

• Lead Free Status / RoHS Status: Compliant

Functional Description
Table 5-60. Output Tag Slot 0
5.22.3
Figure 5-15. AC-Link Powerdown Timing
Intel
®
ICH7 Family Datasheet
When accessing the codec registers, only one I/O cycle can be pending across the AC-
link at any time. The ICH7 implements write posting on I/O writes across the AC-link
(i.e., writes across the link are indicated as complete before they are actually sent
across the link). In order to prevent a second I/O write from occurring before the first
one is complete, software must monitor the CAS bit in the Codec Access Semaphore
register which indicates that a codec access is pending. Once the CAS bit is cleared,
then another codec access (read or write) can go through. The exception to this being
reads to offset 54h/D4h/154h (slot 12) which are returned immediately with the most
recently received slot 12 data. Writes to offset 54h, D4h, and 154h (primary, secondary
and tertiary codecs), get transmitted across the AC-link in slots 1 and 2 as a normal
register access. Slot 12 is also updated immediately to reflect the data being written.
The controller does not issue back to back reads. It must get a response to the first
read before issuing a second. In addition, codec reads and writes are only executed
once across the link, and are not repeated.
AC-Link Low Power Mode
The AC-link signals can be placed in a low-power mode. When the AC ’97 Powerdown
register (26h), is programmed to the appropriate value, both ACZ_BIT_CLK and
ACZ_SDIN will be brought to, and held at a logic low voltage level.
12:
1:0
Bit
15
14
13
3
2
Example
Primary
Access
00
1
1
1
X
0
Note:
BIT_CLK not to scale
BIT_CLK
SDOUT
SDIN
SYNC
Secondary
Example
Access
01
1
0
0
X
0
prev. frame
prev. frame
slot 12
slot 12
Frame Valid
Slot 1 Valid, Command Address bit (Primary codec
only)
Slot 2 Valid, Command Data bit (Primary codec only)
Slot 3–12 Valid
Reserved
Codec ID (00 reserved for primary; 01 indicate
secondary; 10 indicate tertiary)
TAG
TAG
Write to
0x20
Description
Data
PR4
237