CS4239 Datasheet, PDF (89/98 Pages) Cirrus Logic – CrystalClear™ Portable ISA Audio System

CS4239
CrystalClear^TM Portable ISA Audio System
CDROM Interface
The four CDROM pins are multi-function and default to ISA upper address bits SA12-SA15.
To enable the CDROM port, an external 10 kΩ resistor must be tied between MCLK/SCLK
and SGND. MCLK/SCLK is sampled on the falling edge of RESDRV. The alternate CDROM
chip select has its own strapping option to enable ACDCS. Use of the CDROM interface
requires a 1 k E²PROM to support the Plug-and-Play data as well as firmware patch data.
CDCS - CDROM Chip Select, Output, 4 mA drive
This output goes low whenever an address is decoded that matches the value programmed into
the CDROM base address register.
ACDCS - Alternate CDROM Chip Select, Output, 4 mA drive
This pin, XCTL1/ACDCS/DOWN, is multiplexed with two other functions, and defaults to the
XCTL1 output which is controlled by the XCTL1 bit in the WSS I10. This pin can also be
configured at a second CDROM Chip Select, ACDCS, to support the alternate IDE CDROM
decode. To force this pin to the CDROM alternate chip select, an external 10 kΩ resistor must
be tied between SDOUT and SGND. ACDCS output then goes low whenever an address is
decoded that matches the value programmed into the CDROM alternate base address register,
ACDbase. This pin can also be used as the volume up pin DOWN by setting VCEN in Control
register C0 or the Hardware Configuration data. VCEN has the highest precedence over the
other pin functions.
CDINT - CDROM Interrupt, Input
This pin is used to input an interrupt signal from the CDROM interface. The part can be
programmed, through the plug-and-play resource data, to output this signal to the appropriate
ISA bus interrupt line. The polarity if this input can be programmed through CTRLbase+1
register, bit ICH, or the Hardware Configuration data; the default is active high.
CDRQ - CDROM DMA Request, Input
This pin can be used to input the DMA request signal from the CDROM interface. The part can
be programmed, through the plug-and-play resource data, to output this signal to the
appropriate ISA bus DRQ line.
CDACK- CDROM DMA Acknowledge, Output, 4 mA drive
This pin can be used to output the ISA bus-generated DMA acknowledge signal to the CDROM
interface.
DS253PP2
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