CS4237B Datasheet, PDF (24/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
Bytes 19 through 21 map the interrupt number to
the actual interrupt pins A - F. As shown in the
table, the byte 20 default is 0xB9; therefore,
IRQC, which is the lower nibble, maps to the
ISA interrupt 9. Likewise IRQD, which is the
upper nibble, maps to the ISA interrupt 11
(0Bh).
Bytes 22 and 23 map the DMA channel number
to the actual DMA pins A-C. As shown in the
table, the byte 22 default is 0x10; therefore,
DRQA/DACKA is the lower nibble which maps
to the ISA DMA channel 0. Likewise
DRQB/DACKB is the upper nibble which maps
to the ISA DMA channel 1.
Hostload Procedure
This procedure is provided for backwards com-
patibility with the CS4236. Since the E²PROM
allows all resource and firmware patch data to be
loaded at power-up, this procedure is typically
not used. To download PnP resource data from
the host to the part’s internal RAM, use the fol-
lowing sequence:
1. Configure Control I/O base address,
CTRLbase, by one of two methods: regular
PnP cycle or Crystal Key method.
a. The host can use the regular PnP cycle to
program the CTRLbase, and then place the
chip in the wait_for_key_state
b. If the Crystal Key method is used:
First, send the 32-byte Crystal key to I/O
address 0279h. (The Crystal Key only
supports one Crystal part per system.)
Second, configure logical device 2 base
address, CTRLbase, by writing to I/O
0279h (15h, 02h, 47h, xxh, xxh, 33h,
01h, 79h).
Note: The two xxh represent the base_ad-
dress_high and base_address_low
respectively. The default is: 01h, 20h.
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2. Write 57h (Jump to ROM) command to
CTRLbase+5.
3. Download the PnP resource data.
a. Send download command by writing AAh
to CTRLbase+5.
b. Send starting download address (4000h)
by writing low byte (00h) first, and then
high byte (40h) to CTRLbase+5.
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.
4. End download by writing 00h to
CTRLbase+6.
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 Crystal part, and
firmware patches to upgrade the core processor
functionality.
DS213PP4