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Texas Instruments Incorporated

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GC2011A 3.3V DIGITAL FILTER CHIP

SLWS129A

This document contains information which may be changed at any time without notice

3.0

FILTERING MODES

This Section describes common filtering modes and how to configure the chip to implement them. Unless

otherwise indicated, only the A-path, B-path and cascade mode control register values are given. The counter, gain,

output, and snapram control registers can be given the default values listed in Table 1 below.

The default settings configure the chip to:

•

Use the A-in pins for the cascaded mode data input and the B-out pins for the cascaded

mode data output. The cascaded mode results can be output on the A-out pins by

setting the OUTPUT register to 0008HEX.

•

Round the outputs to 16 bits.

•

Give an input to output gain of

The input to output latency is given for each of the modes. The latency is due to pipeline delays and is defined

as the delay from x0 (see Figure 6-a) to the first filter output affected by x0. One can measure this delay by clearing all

of the filter taps except for the first tap and using an impulse as the data input. The latency is then defined as the delay

in clock cycles (not data samples) from the impulse in to the impulse out

The modes described in this Section have been configured so that the input and output timing is as shown in

Figure 6. In the half rate and quarter rate modes the inputs must be synchronized with SI as shown. The output timing

shows how the output samples are generated relative to SI.

Figure 6. I/O Timing

Table 1: Default Control Register Settings

DEFAULT

COMMENT

COUNTER

Don’t care

GAIN

1030

See Section 6.5

OUTPUT

See Section 6.6

SNAP_REGA

See Sections 6.7 and 6.8 to

configure the snapshot memory

SNAP_REGB

SNAP_REGC

2 13

–

()

∑

012345

6789

TIME

Full Rate

Half Rate

Quarter Rate

Full Rate

Half Rate

Quarter Rate

(a) INPUT TIMING

(b) OUTPUT TIMING

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