CS4237B Datasheet, PDF (105/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
CDROM and Modem Interface
The four CDROM pins are multi-function and default to ISA upper address bits SA12-SA15.
To enable the CDROM port, an external 10kΩ resistor must be tied between XIOR and SGND.
XIOR is sampled on the falling edge of RESDRV. If the CDROM interface doesn’t support
DMA, the two CDROM DMA pins can be converted to support Logical Device 5, a modem
interface.
CDCS - CDROM Chip Select, Output, 4mA 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, 4mA drive
This pin, XCTL1/SINT/ACDCS/DOWN, is multiplexed with three 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. The pin is switched to the CDROM alternate chip select when the base address
ACDbase is first programmed to non-zero through the E²PROM data or PnP commands. This
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/MINT - CDROM DMA Request, or Modem Interrupt, 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.
This pin can also be used to input an interrupt signal from a modem. The pin is switched to
MINT when the LD5 base address, COMbase, is first programmed to non-zero through the PnP
data or a hostload. The polarity of MINT can be programmed through CTRLbase+1 register,
IMH bit, or the Hardware Configuration data; the default is active low.
CDACK/MCS - CDROM DMA Acknowledge, or Modem Chip Select, Output, 4mA drive
This pin can be used to output the ISA bus-generated DMA acknowledge signal to the CDROM
interface. Alternately, this pin can be used to output an active low Modem chip select, MCS.
The pin is switched to the modem chip select when the LD5 base address, COMbase, is first
programmed to non-zero through the PnP data or a hostload.
DS213PP4
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