CS4237B Datasheet, PDF (16/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
3. A unique identifier (handle) is assigned to the
part and the resource data is read.
4. After all cards’ resource requirements are de-
termined, the host uses the handle to assign
conflict-free resources
5. After the configuration registers have been
programmed, each configured logical device
is activated.
6. The part is then removed from Plug-and-Play
mode.
Upon power-up, the chip is inactive and must be
enabled via software. The Crystal part monitors
writes to the PnP Auto-Configuration Address
port (0279h). If the host sends a PnP initiation
key, consisting of a series of 32 predefined byte
writes, the hardware will detect the key and
place the part into the Plug-and-Play (PnP)
mode. Another method to program the part is to
use a special Crystal initiation key which func-
tions like the PnP initiation key, but can be
invoked by the user at any time. However, the
Crystal Key only supports one Crystal part per
system. The Crystal key and special commands
are detailed in the Crystal Key and Bypassing
PnP sections.
The isolation sequence uses a unique 72-bit se-
rial identifier. The host performs 72 pairs of I/O
read accesses to the Read Data port. The identi-
fier determines what data is put on the data bus
in response to those read accesses. When the iso-
lation sequence is complete, the CM assigns a
Card Select Number (CSN) to the part. This
number distinguishes the Crystal part from the
other PnP devices in the system. The Configura-
tion Manager (CM) then reads the resource data
from the Crystal part. The 72-bit identifier and
the resource data is either stored in an external
user-programmable E²PROM, or loaded via a
"hostload" procedure from BIOS before PnP
software is initiated.
The CM determines the necessary resource re-
quirements for the system and then programs the
part through the configuration registers. The con-
figuration register data is written one logical
device at a time. After all logical devices have
been configured, CM activates each device indi-
vidually. Each logical device is now available on
the ISA bus and responds to the programmed
address range, DMA channels, and interrupts that
have been allocated to that logical device.
PnP Data
Hardware Configuration and Plug-and-Play re-
source data must be loaded into the part’s RAM.
The data may be stored in an external E²PROM
or may be downloaded from the host.
To load the data, refer to the Loading Resource
Data section. The following is the Plug-and-Play
resource data:
The first nine bytes of the PnP resource data are
the Plug-and-Play ID, which uniquely identifies
the Crystal part from other PnP devices. The
Crystal default is broken down as follows:
0Eh, 63h - Crystal ID - ’CSC’ in compressed
ASCII. (See the PnP Spec for more
information)
42h - Oem ID. A unique Oem ID must be ob-
tained from Crystal for each unique
Crystal product used.
37h - Crystal product ID for the CS4237B
FFh, FFh, FFh, FFh - Serial number. This can
be modified by each OEM to uniquely
identify their card.
??h - Checksum.
Of the 9-byte serial number listed above, Crystal
software uses the first two bytes to indicate the
presence of a Crystal part, and the fourth byte,
0x37, to indicate the CS4237B; therefore, these
three bytes must not be altered.
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