CS4239 datasheet(22/98 Pages) CIRRUS

22 / 98 page

(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 must al-

ways be written as 0), "rbc" is used for

"reserved, backwards compatible" for bits that

were used on previous chips, but are no longer

required on this chip. These bits are read/wri-

table but should generally be set to 0 for

backwards compatibility.

BYTE

Default

Description

155h

2PROM validation byte 1.

The first two bytes indicate that the E

2PROM exists.

BBh

2PROM validation byte 2

00h

High byte for length of data in E

2PROM

DDh

Low byte for length of data in E

2PROM

00h

Alternate CDROM (Logical Device 4), ACDbase, Address length mask

03h

RESERVED

80h

Misc. Configuration Bits: CDROM Interrupt Polarity, Key Disables, VCEN

00h

Global Configuration Byte: IFM, VCF1, WTEN

05h

Code Base Byte

20h

FM Volume Scaling

11*

04h

RESERVED - Must be 0x04

12*

08h

RESERVED - Must be 0x08

13*

10h

RESERVED - Must be 0x10

80h

Mono and DSP Port Control

00h

2PROM Checksum

00h

Global Configuration Byte 2: EECS, AUX1R, 3DEN, DSPD1, PSH

08h

CDROM (Logical Device 4), CDbase, Address length

18*

48h

RESERVED - Must be 0x48

75h

IRQ A/B Selection: Lower nibble = A, Upper nibble = B.

Along with next two bytes - specify hardware interrupts tied to IRQA-IRQF pins

B9h

IRQ C/D Selection: Lower nibble = C, Upper nibble = D.

FCh

IRQ E/F Selection: Lower nibble = E, Upper nibble = F.

10h

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

03h

DMA C/IRQ G Selection: Lower nibble = DMA C, Upper nibble = IRQ G

NOTE:The first four bytes are exclusive to the E

2PROM 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

DS253PP2

CS4239

CrystalClear Portable ISA Audio System

CS4239 Datasheet(PDF) 22 Page - Cirrus Logic

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