CS4239 Datasheet, PDF (26/98 Pages) Cirrus Logic – CrystalClear™ Portable ISA Audio System

CS4239
CrystalClear^TM Portable ISA Audio System
c. Send the Hardware Configuration and re-
source data in successive bytes to
CTRLbase+5. This includes the Hardware
Configuration and the PnP resource data.
The PnP resource format is described in
the PnP Data section. The resource header
should not contain the first four bytes
which are only used for E²PROM loads.
d. End download by writing 00h to
CTRLbase+6.
4. Download Firmware data. To download
firmware data, contact Cirrus Logic for the
ISA Audio BIOS kit.
5. If any of the Hardware Configuration Data
(first 19 bytes) has changed, 5Ah must be
written to CTRLbase+5 to force the part to
internally update this information.
The new PnP data is loaded and the part is ready
for the next PnP cycle.
External E²PROM
The Plug and Play specification defines 32 bits
of the 72-bit Serial Identifier as being a user de-
fined serial number. The E²PROM is used to
change the user section of the identifier, store
default resource data for PnP, Hardware Con-
figuration data specific to the CS4239, and
firmware patches to upgrade the core processor
functionality.
The E²PROM interface uses an industry standard
2-wire interface consisting of a bi-directional
data line and a clock line driven from the part.
After power-on the part looks for the existence
of an E²PROM device and loads the user de-
fined data. The existence is determined by the
first two bytes read (0x55 followed by 0xBB). If
the first two bytes are correct, the part reads the
next two bytes to determine the length of data in
the E²PROM. The length bytes indicate the
number of bytes left to be read (not including
26
the two validation bytes or two length bytes). As
shown in Figure 3, the E²PROM is read using a
start bit followed by a dummy write, to initialize
the address to zero. Then another start bit and
device address, followed by all the data. Since
the part uses the sequential read properties of the
E²PROM, only one E²PROM, is supported
(ganged E²PROMs are not supported).
Some E²PROMs that are compatible with this
interface are:
Atmel
AT24Cxx series
MicroChip
24LCxxB series
National
NM24CxxL series
Ramtron
FM24Cxx series
SGS Thompson ST24Cxx series
Xicor
X24Cxx series
where the xx is replaced by 02, 04, 08, or 16
based on the size of the E²PROM desired. The
size of 08 (1k bytes) is preferred since it allows
the maximum flexibility for upgrading firmware
patches. Other E²PROMs compatible with Fig-
ure 3 and the timing parameters listed in the
front of the data sheet may also be used.
The maximum Hardware Configuration and PnP
resource RAM data supported is 384 bytes, and
a four byte header; therefore, the maximum
amount of data storage, without firmware
patches, in E²PROM would be 388 bytes. The
maximum size E²PROM needed is 770 bytes, to
allow the inclusion of firmware patches after the
PnP resource data.
If an external E²PROM exists, it is accessed by
the serial interface and is connected to the SDA
and SCL pins. The two-wire interface is control-
led by three bits in the Control logical device,
Hardware Control Register (CTRLbase+1). The
serial data can be written to or read from the
E²PROM by sequentially writing or reading that
register. The three register bits, D0, D1, D2 are
labeled CLK, DOUT, and DIN/EEN respectively.
The DIN/EEN bit, when written to a one, en-
ables the E²PROM serial interface. When the
DIN/EEN bit is written to a zero, the serial inter-
DS253PP2