SAA2032 Datasheet, PDF (7/28 Pages) NXP Semiconductors – Digital equalization for the tape drive processing of the DCC system

Philips Semiconductors
Digital equalization for the tape
drive processing of the DCC system
Product specification
SAA2032
FUNCTIONAL DESCRIPTION
Operating Modes
DEQ operating modes are programmed via the LT
interface:
NORMAL
• A/D conversion
• Demultiplexing
• Equalization
• Zero crossing.
in this mode the SAA2032 performs the equalization and
slicing of the eight data channels and the auxiliary channel.
The eight data channels have a bit-rate of 96 kbits/s while
the auxiliary channel has a bit-rate of 12 kbits/s.
The SAA2032 input is a time-multiplexed analog signal
from the Read Amplifier. The signal contains ten time slots,
of which nine are used. The Read Amplifier and the
SAA2032 synchronize with the RDCLK and RDSYNC
signals generated by the SAA2032.
Following A/D conversion and demultiplexing the nine
channels are equalized. The encoding of the equalizing
coefficients (12 per channel) are not fixed and must be
loaded via the LT interface before operation.
The nine equalized output signals are up-sampled by a
factor of 10 with the resulting signals fed to the slicer. The
slicer output is applied to the SAA2022.
TEST
• A/D conversion
• Demultiplexing
• Equalization
• Zero crossing
• Eye-pattern.
Same as normal mode. In addition the digital and analog
eye-pattern outputs are enabled. The eye-pattern output
corresponds to one of the equalized channel outputs.
SEARCH
• A/D conversion
• Envelope detection
• Tape search and speed measurement.
In the search mode the analog input signal from the Read
Amplifier is not the multiplexed signal but only the auxiliary
channel signal.
Following A/D conversion the envelope of this signal is
filtered and sliced. This forms the Alternating Envelope
AENV output. The LABEL and VIRGIN outputs are
detected from this and the tape search speed measured.
OFF
In the OFF mode the RDSYNC and RDCLK signals are
HIGH, the EYE outputs are disabled and the channel and
auxiliary outputs (CH0 to CH7 and AUX) are 3-stated.
Read Amplifier interface
The interface between the Read Amplifier and the
SAA2032 consists of three signals:
1. VIN from Read Amplifier to SAA2032; time
multiplexed data.
2. RDSYNC from SAA2032 to Read Amplifier;
synchronization between Read Amplifier multiplexer
and SAA2032 demultiplexer.
3. RDCLK from SAA2032 to Read Amplifier; data clock
for Read Amplifier multiplexer.
The multiplexed VIN output of the Read Amplifier changes
to another channel at the rising edge of RDCLK. RDSYNC
synchronizes the Read Amplifier VIN output: if RDSYNC is
HIGH, the rising edge of the RDCLK will select the AUX
channel.
Figures 4 and 5 show the relationship between the
SAA2032 and the Read Amplifier.
SAA2022 interface
The interface with the SAA2022 consists of the 9 data
output signals CH0 to CH7, AUX.
Table 1 Dependency of Read Amplifier on
operational mode.
OPERATIONAL MODE
Normal
Test
Search
Off
RDSYNC
YES
YES
HIGH
HIGH
RDCLK
YES
YES
YES
HIGH
Label and virgin detection interface
When the DCC player is in its search mode, the tape is
fast-wound while the head retains tape contact. The
SAA2032 can be made to operate in the search mode and
the information will be read from the auxiliary tape track.
February 1995
7