GC1012A Datasheet, PDF (27/30 Pages) Texas Instruments – DIGITAL TUNER CHIP

GC1012A DIGITAL TUNER
DATA SHEET REV 0.1
5.5 SYNCHRONIZING MULTIPLE GC1012A CHIPS
A system containing a bank of GC1012A chips will need to be synchronized so that the output
frames from each chip are aligned, and, if desired, so that their frequency accumulators are running
synchronously. The GC1000 Input Switch chip has built in sync counters which are designed specifically for
this purpose. If the GC1000 chip is not used, then the one-shot strobe (see Section 3.7) can be used. The
bank of chips should be interconnected so that the OS pin of one GC1012A chip is tied to the SS input of
all of the chips. The one-shot strobe mode can then be used to simultaneously synchronize all of the chips.
The OS pin of a second GC1012A chip should be tied to the AS input of all of the chips. The one-shot mode
of the second chip can be used to synchronize the frequency accumulators whenever the tuning frequency
has been changed.
5.6 PROCESSING COMPLEX DATA
Two GC1012A chips can be used to process complex input data by using one chip to process the
I-input data and the other to process the Q-input data. If the two chips are synchronized as discussed above,
then the complex output stream can be reconstructed by adding and subtracting the I and Q outputs of the
two chips. A programmable gate array chip such as from XILINX would be ideal for this post-processing.
The configuration for processing complex data is illustrated in Figure 6.
I_IN
X
I
GC1012A ^Q
SS
AS
OS
I_OUT
Q_IN
X
I
Q_OUT
GC1012A ^Q
SS
AS
OS
PROGRAMMABLE
GATE
ARRAY
Figure 6. Processing Complex Input Data
GRAYCHIP,INC.
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FEBRUARY 18, 1998
This document contains information which may be changed at any time without notice