NS32FV100 Datasheet, PDF (14/96 Pages) Texas Instruments – NS32FX100 NS32FV100 NS32FX200 System Controller

2 0 Architecture (Continued)
After reset RFRT is initialized to 6
 Programmable IIR filters
RFEN
7
res
Writing to RFRT must be followed by read back
to ensure that the RFRT has in fact been up-
dated This procedure must be repeated until
RFRT is updated (value read e value written)
RFRT exists only in the NS32FV100 and the
NS32FX200
Refresh enable
6
5
0
EN
res
Programmable transmit filters
Programmable receive filters
Programmable echo canceling filter
 Programmable gain control
 Programmable fine timing tuning
 Digital loop-back mode
 Reduced CPU load by 12-level transmission FIFO and 12-
level reception FIFO
2 3 2 Operation
EN 0 No refresh transactions
The Sigma Delta CODEC performs high resolution analog-
1 Refresh transactions are issued by
to-digital (A D) and digital-to-analog (D A) conversions us-
the chip according to the refresh
ing an over sampling technique This module is optimized
rate selected by RFRT
After reset EN is set to ‘‘1’’
RFEN exists only in the NS32FV100 and the
NS32FX200
2 2 3 1 Usage Recommendations
The ECOUNT bit in MCFG must be set to enable TCU
counters operation
te ^{2 3 SIGMA-DELTA CODEC (SDC)}
2 3 1 Features
 16-bit format Analog-to-Digital converter and Digital-to-
Analog converter
 Full and Half Duplex operation
 Optimized for FAX and DATA Modems
le ^{ Various sampling rates for voice and data applications}
Obso ^{ Total harmonic distortion better than b70 dB}
for use as the analog front end for Digital Signal Processing
(DSP) applications such as modems or voice processing
The SDC’s main advantage compared to other A D and
D A convertors is the use of digital circuitry resulting in high
reliability and reduced cost The SDC solution incorporates
a second-order digital Sigma-Delta modulator and a noise
shaping technique to improve performance
The digital parts of the converters are implemented on-chip
and a few external components implement the analog parts
NSFAX Software package fully supports the SDC Software
drivers handle both the SDC initialization and data transfers
National Semiconductor’s modem software is usually pro-
vided in binary form and hence the internal structure of the
SDC is transparent to the user A detailed description of the
SDC is available only for source-level customers
2 3 2 1 Block Diagram
The Sigma-Delta CODEC block diagram is shown in Figure
2-4
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