GC5316 datasheet(17/75 Pages) TI

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GC5316

SLWS154A − JANUARY 2004 − REVISED MARCH 2004

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CN/2 −1

C N−1

CN/2

PF IR

PF I R

From CF IR

First Half Coefficients

Second Half Coefficients

Tap Delay

DDC 2K

DDC 2K+1

Figure 14. Double Tap Mode Interconnect

When in double-tap mode, the first half of the coefficients should be loaded into the even DDC, the remaining

coefficients go into the odd DDC. The even DDC must be turned on (ddc_duc_ena 1), and the odd DDC must be

turned off (ddc_duc_ena 0).

For strapped UMTS with double length filters, the range of taps available is 56 to 128 in increments of eight.

PFIR coefficients and gain shift values are shared between both A and B CDMA channels in a DDC block. The

number of maximum taps available for double length UMTS mode is:

Double Length UMTS Mode: 8 x (rxclk

÷ output sample rate)

Table 16. Programming

VARIABLE

DESCRIPTION

crastsrttap_pfir(3:0)

Number of DDC PFIR filter taps is 4(crastartap+1)

For double-length PFIR the number of taps is 8(crastartap+1)

pfir_gain(2:0)

Sets the gain of the PFIR filter.

double_tap

When set, puts two adjacent DDC (2k and 2k+1, k = 0 to 5) in 127 tap UMTS mode.

Set to 0 for normal mode.

Set to 2 for the main (even) DDC

Set to 1 for the secondary (odd) DDC.

When in double tap mode, the first half of the coefficients should be loaded into the even DDC, the

remaining coefficients go into the odd DDC.

ALSO: In double tap mode, the even DDC must be turned on (ddc_duc_ena 1), and the odd DDC

must be turned off (ddc_duc_ena 0).

The PFIR filter’s 18-one integer coefficient per line. Note that the PFIR filter coefficients are shared

by the A and B channels in CDMA mode.

Note: that the above PFIR filter coefficients are shared between both A and B sides of a DDC block.

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