876784 Intel, 876784 Datasheet - Page 239

• Manufacturer Part Number: 876784
• Manufacturer: Intel

Specifications of 876784

• Lead Free Status / RoHS Status: Compliant

Functional Description
5.22.4
5.22.5
Note:
5.22.6
Intel
®
ICH7 Family Datasheet
AC ’97 Cold Reset
A cold reset is achieved by asserting ACZ_RST# for 1 µs. By driving ACZ_RST# low,
ACZ_BIT_CLK, and ACZ_SDOUT will be activated and all codec registers will be
initialized to their default power on reset values. ACZ_RST# is an asynchronous AC ’97
input to the codec.
AC ’97 Warm Reset
A warm reset re-activates the AC-link without altering the current codec register
values. A warm reset is signaled by driving ACZ_SYNC high for a minimum of 1 µs in
the absence of ACZ_BIT_CLK.
Within normal frames, ACZ_SYNC is a synchronous AC ’97 input to the codec. However,
in the absence of ACZ_BIT_CLK, ACZ_SYNC is treated as an asynchronous input to the
codec used in the generation of a warm reset.
The codec must not respond with the activation of ACZ_BIT_CLK until ACZ_SYNC has
been sampled low again by the codec. This prevents the false detection of a new frame.
On receipt of wake up signaling from the codec, the digital controller issues an interrupt
if enabled. Software then has to issue a warm or cold reset to the codec by setting the
appropriate bit in the Global Control Register.
Hardware Assist to Determine ACZ_SDIN Used Per Codec
Software first performs a read to one of the audio codecs. The read request goes out on
ACZ_SDOUT. Since the ICH7 allows one read to be performed at a time on the link,
eventually the read data will come back in on one of the ACZ_SDIN[2:0] lines.
The codec does this by indicating that status data is valid in its TAG, then echoes the
read address in slot 1 followed by the read data in slot 2.
The new function of the ICH7 hardware is to notice which ACZ_SDIN line contains the
read return data, and to set new bits in the new register indicating which ACZ_SDIN
line the register read data returned on. If it returned on ACZ_SDIN[0], bits [1:0]
contain the value 00. If it returned on ACZ_SDIN[1], the bits contain the value 01, etc.
ICH7 hardware can set these bits every time register read data is returned from a
function 5 read. No special command is necessary to cause the bits to be set. The new
driver/BIOS software reads the bits from this register when it cares to, and can ignore
it otherwise. When software is attempting to establish the codec-to-ACZ_SDIN
mapping, it will single feed the read request and not pipeline to ensure it gets the right
mapping, we cannot ensure the serialization of the access.
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