CS4235 Datasheet, PDF (21/94 Pages) Cirrus Logic – CrystalClear Low Cost ISA Audio System

CS4235
CrystalClear ^TM Low Cost ISA Audio System
(Hostload), the first four bytes are not needed;
therefore, the configuration data is only 19 bytes
long. The configuration data maps the many
functions of the logical devices to the physical
pins of the chip. Table 2 lists the Hardware Con-
figuration bytes. The detailed bit descriptions for
each byte follows. While the reserved bits are
listed as "res" in the bit position (and should be
written to 0), "rbc" is "reserved, backwards com-
patible" for bits that were used on previous
chips, but are no longer required on this chip.
These bits are read/writable but should generally
be set to 0 for backwards compatibility.
BYTE Default
1
55h
2
BBh
3
00h
4
DDh
5
00h
6
03h
7
80h
8
00h
9
05h
10
20h
11*
04h
12*
08h
13*
10h
14
80h
15
00h
16
00h
17
08h
18*
48h
19
75h
20
B9h
21
FCh
22
10h
23
03h
Description
E²PROM validation byte 1.
The first two bytes indicate that the E²PROM exists.
E²PROM validation byte 2
High byte for length of data in E²PROM
Low byte for length of data in E²PROM
Alternate CDROM (Logical Device 4), ACDbase, Address length mask
RESERVED
Misc. Configuration Bits: CDROM Interrupt Polarity, Key Disables, VCEN
Global Configuration Byte: IFM, VCF1, WTEN
Code Base Byte
FM Volume Scaling
RESERVED - Must be 0x04
RESERVED - Must be 0x08
RESERVED - Must be 0x10
Mono and DSP Port Control
E²PROM Checksum
Global Configuration Byte 2: EECS, AUX1R, 3DEN, DSPD1, PSH
CDROM (Logical Device 4), CDbase, Address length
RESERVED - Must be 0x48
IRQ A/B Selection: Lower nibble = A, Upper nibble = B.
Along with next two bytes - specify hardware interrupts tied to IRQA-IRQF pins
IRQ C/D Selection: Lower nibble = C, Upper nibble = D.
IRQ E/F Selection: Lower nibble = E, Upper nibble = F.
DMA A/B Selection: Lower nibble = A, Upper nibble = B.
This byte and the next byte specify hardware DRQ/DACKs tied to the DMAA-DMAC pins
and the 7th IRQ pin - IRQ G
DMA C/IRQ G Selection: Lower nibble = DMA C, Upper nibble = IRQ G
NOTE:The first four bytes are exclusive to the E²PROM and are not used in the Hostload mode.
* Currently not supported. Must be set to default values given in the table.
Table 2. Hardware Configuration Data
DS252PP2
21