CS4237B Datasheet, PDF (112/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
APPENDIX B: DIFFERENCES BETWEEN THE CS4236 AND THE CS4237B
This part is designed to be hardware and software backwards compatible with the CS4236 and will
drop into an existing CS4236 socket without any hardware modifications. Properly written code for the
CS4236 will run on the this Codec. However, the CS4237B has enhancements over the CS4236 that
provide extra functionality.
The differences are as follows:
1. CTRLbase+3 is redefined to be an indirect address register and CTRLbase+4 is redefined to be an
indirect data register. These registers allows access to C0 through C8 indirect registers.
2. CDSDD in the Global Configuration byte of the Hardware Configuration data has been renamed
SDD and its function expanded. On this part, setting SDD disables peripheral port reads from driv-
ing the ISA data bus for ALL peripheral port devices, e.g. CDROM and MODEM. On the CS4236,
setting CDSDD disables peripheral port reads for the CDROM device ONLY.
3. The Serial Port works continuously once enabled. CEN and PEN do not have any effect on the se-
rial port. On the CS4236, CEN and PEN disabled their respective part of the serial port when set to
zero.
4. The GAME Logical Device (Joystick) only aliases from GAMEbase+0 to GAMEbase+5. GAME-
base+6 and GAMEbase+7 are reserved. This Codec also contains support for Digital Assist of
analog joysticks to support the Microsoft Direct Input initiative.
5. I25 was defined as a Version and Chip ID register in the CS4236. This register is now redefined as
a Compatibility register and is identical to the CS4236 to allow software written to the CS4236 to
work properly on this part. The Version and Chip ID for this chip has been moved to Control indi-
rect register C1 and WSS indirect register X25 (Revision C or greater).
6. I27 and I29 in the WSS space are reserved.
7. When IFM is enabled (and remapping is enabled) I18/I19 return the same value written when mute
is enabled. On the CS4236, I18/19 returns 0xBF when mute is enabled.
8 The OLB bit in I16 is no longer functional and internally is set as if OLB is on.
9. The MIC input impedance is now 8 kΩ minimum.
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