Cirrus Logic CS6422 - Manual

Copyright
© Cirrus Logic, Inc. 2006
(All Rights Reserved) http://www.cirrus.com
CS6422
Technical Brief
UPGRADING FROM THE CS6420 TO THE CS6422
This document contains information that is useful
in transitioning a system from the CS6420 to the
CS6422.
Performance Differences
The analog and echo cancelling performance of the
CS6422 is identical to the CS6420. The CS6422 in-
corporates a super-set of features and enhanced
configuration options.
Board-level Changes
The CS6420 and CS6422 are 100% pin compatible.
No board-level changes are necessary (or recom-
mended) for migrating to the CS6422. However,
any circuitry added to a CS6420 system to imple-
ment an external sidetone can be eliminated (or re-
main unpopulated) if the internal programmable
sidetones on the CS6422 are used.
Register Definition Changes
A number of CS6420 register bit fields have been
renamed and some of the definitions and values
have been modified in the CS6422. The register
mapping (location and decoding of registers) is
completely new.
The CS6422 register map provides for 4 bits of ad-
dress decoding (compared to 3 bits in the case of the
CS6420), or 8 independent addresses (bit 0 is al-
ways ‘0’), 6 of which are implemented. Each regis-
ter contains 12 bits of configuration information.
Furthermore, all but one of the bit fields reside on
nibble boundaries, making conversions to and from
hexadecimal very convenient.
The following table summarizes the bit fields that
have changed:
New Register/Feature Additions:
1) Explicit disable controls AECD and NECD
have been added to disable the acoustic and net-
work echo cancellers independently. In the
CS6420, the network canceller is disabled by
allocating all the Taps to the AEC. In the
CS6422, the NEC is disabled by setting NECD.
The Taps parameter can be set to any allowed
value.
2) Auto network path detect. The CS6422 is able
to detect when a network path is present or ab-
sent and can automatically enable or disable the
network echo canceller as appropriate, even
during a call in progress. To enable this feature,
NFNse should be set to a non-zero value (this
allows the NEC to be disabled if a network path
CS6420
Reg
CS6422
Reg
CS6420
Values
CS6422
Values
CS6422
Default
HD HDD same same same (Half
duplex
allowed)
RVol RVol -60dB to
+30dB
-12dB to
+30dB
same
(+18dB)
TVol TVol -60dB to
+30dB
-12dB to
+30dB
same
(0dB)
THDet THDet 3,5,6dB 6,9,12dB 6dB
RHDet RHDet 3,5,6dB 6,9,12dB 6dB
RSThd RSThd 3,5,6dB 6,9,12dB 6dB
Taps Taps 55.5/--- ms 55.5/8 ms same
(39.5/24 ms)
NseRmp NseRmp 1.5,3,6dB/s 3,6,12dB/s same
(3dB/s)
TSThd TSThd 9,12,15dB 9,12,15,
18dB
same
(15dB)
MAR ‘06
DS295TB2