CS4237B Datasheet, PDF (17/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
The next 3 bytes are the PnP version number.
The default is version 1.0a: 0Ah, 10h, 01h.
The next sequence of bytes are the ANSI identi-
fier string. The default is: 82h, 0Eh, 00h,
’Crystal Codec’, 00h.
The logical device data must be entered using
the PnP ISA Specification format. Typical logical
device values are found in Table 1. The
E²PROM version for this data is found in Ap-
pendix A.
Loading Resource Data
A serial E²PROM interface allows user-program-
mable serial number and resource data to be
stored in an external E²PROM. The interface is
compatible with devices from a number of ven-
dors and the size may vary according to specific
customer requirements. The maximum size for
resource data supported by the part’s internal
RAM is 384 bytes of combined Hardware Con-
figuration and PnP resource data. With the
addition of the 4-byte header, the maximum
amount of E²PROM space used would be 388
bytes. However, the part also supports firmware
upgrades via the E²PROM. The maximum size
E²PROM supported is 2k bytes. After power-up,
the existence of an E²PROM is checked by read-
ing the first two bytes from the E²PROM
interface. If the data from the E²PROM port
reads 55h and BBh, then the rest of the
E²PROM data is loaded into the internal RAM.
If the first two bytes aren’t correct, the E²PROM
is assumed not to exist and a "hostload" proce-
dure must be used to load the internal RAM. The
Hostload procedure can be found in the Hostload
section. For motherboard designs, an E²PROM
should still be included, to allow faster integrat-
ing of resource and firmware patch data. This
allows updates without respiring BIOS code. If
the part is installed on a plug-in card, then an
external E²PROM is required to ensure that the
proper PnP resource data is loaded into the inter-
nal RAM prior to a PnP sequence. See the
External E²PROM section for more information
on the serial E²PROM interface and E²PROM
programming.
The format for the data stored in the E²PROM is
as follows:
(Hardware Configuration Data:)
2 bytes E²PROM validation: 55h, BBh
2 bytes length of resource data in E²PROM
19 bytes Hardware Configuration
(Plug and Play Resource Data:)
9 bytes Plug and Play ID
3 bytes Plug and Play version number
Variable number of bytes of user defined
ASCII ID string
Logical Device 0 (Windows Sound System,
FM Synthesizer, Sound Blaster Pro) data
Logical Device 1 ( Game Port) data
Logical Device 2 ( Control) data
Logical Device 3 ( MPU-401) data
Logical Device 4 ( CD-ROM) data
Logical Device 5 (Modem) data
End of Resource byte & checksum byte
Firmware patch code.
A typical E²PROM data load, in assembly for-
mat, can be found in Appendix A.
Loading Firmware Patch Data
An external E²PROM is read during the power-
up sequence that stores Hardware Configuration
and PnP data, and firmware patch data. The part
contains RAM and ROM to run the core proces-
DS213PP4
17