CS4235 Datasheet, PDF (93/94 Pages) Cirrus Logic – CrystalClear Low Cost ISA Audio System

CS4235
CrystalClear ^TM Low Cost ISA Audio System
APPENDIX B: DIFFERENCES BETWEEN THE CS423xB DEVICES AND THE CS4235
This part is designed to be hardware backwards compatible with some CS423xB designs, primarily
motherbaord applications. New drivers will be needed to support this part.
Hardware Pin Differences:
1. RFILT and LFILT capacitors are no longer needed and should be removed. On the CS4235, these
pins are renamed FLTI and FLTO and should have a capacitor placed between them. They are used
for the Crystal 3D Sound circuitry. Not populating this capacitor will not have any adverse affects
on the part, but will result in non-optimum 3D Sound.
2. The external L/RLINE analog inputs are no longer supported. LLINE is now FLT3D and is used
for the 3D Sound function. A 0.01 µF capacitor should be placed between this pin and analog
ground. When external analog wavetable is desired, the AUX1 analog inputs should be used.
3. The analog microphone inputs are now mono. LMIC is changed to MIC, and RMIC has been re-
moved.
4 Mono Out, MOUT, has been removed. The pin is redefined as APSEL and used to change the Ad-
dress Port. APSEL has an internal pullup, setting the Address Port to 0x279 for backwards
compatibility.
5. VDF4 has been changed to IRQG - a seventh interrupt (typically used for INT 10). The default is
disabled to provide backwards compatibility.
6. The Modem Logical Device has been removed. This includes MCS and MINT.
7. Support for an external synthesizer has been removed. This includes SCS and SINT.
8. The peripheral port has been removed. This includes XD<7:0>, XIOR, XIOW, XA<0:2>. CDROM
applications must now drive the ISA bus directly or through buffers.
9. The hardware strap enable for the CDROM has been moved. CS423xB designs have a pulldown on
XIOR. To support the CDROM interface on the CS4235, the pulldown must be moved to the
MCLK pin. Also, to enable the alternate CDROM chip select pin ACDCS, a pulldown must be
added to pin SDOUT.
10. The DSP serial port is no longer supported as an option on the 2nd Joystick connector. The DSP
port is still located on pins 4 through 7.
11. There is no 3.3 V ISA support.
12. The consumer IEC-958 (S/PDIF) output, supported on the CS4237B and CS4238B, has been re-
moved.
13. Only two modes of Hardware Volume Control are supported: 2-button, and 3-button with momen-
tary mute. In addition, a 10 nF capacitor to ground is required for switch debounce on the CS4235.
14. Pullup resistors have been added to the 4 Joystick Button pins, 3 Hardware Volume Control pins,
and the MIDIN pin.
DS252PP2
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