GC5316_14 Datasheet, PDF (7/76 Pages) Texas Instruments – HIGH-DENSITY DIGITAL DOWNCONVERTER AND UPCONVERTER

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2.2 DDC Organization
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F ro m Inp ut ¹⁸
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I nte rface ₁₈
GC5316
SLWS154A − JANUARY 2004 − REVISED MARCH 2004
4 to 1
Sw itch
C DMA DDC A
4 to 1
S wi tch
C DMA DDC B
DD C 0
DD C 1
DD C 2
DD C 3
DD C 4
DD C 5
DD C 6
DD C 7
DD C 8
DD C 9
DD C 10
DD C 11
Figure 5. Receive DDC Blocks
The GC5316 provides downconversion for up to 24 CDMA2000 receive channels or 12 UMTS receive channels.
Downconversion channels are organized into 12 DDC blocks. Each DDC block provides two CDMA2000 DDC
channels, A and B, or one UMTS channel. Each DDC block has its own register set and may be programmed
independently (except for parameters specifying the configuration of the rx_distribution bus).
Two DDC blocks (for example, DDC 0 and DDC 1) can be strapped together to form a single UMTS DDC channel
with double-length filtering. The GC5316 can therefore provide six UMTS DDC channels with double-length FIR
filtering.
Configuration parameters ending in _a apply to the A CDMA channel or to the UMTS channel. Parameters ending
in _b apply the B CDMA channel and are unused in UMTS mode. Many parameters are shared between the A and
B channels in CDMA mode (such as filter coefficients), while key parameters are independent for the two channels
(such as frequency, phase, and gain).
Both CDMA DDC channels in a block can be independently tuned, though they would likely be used as diversity pairs
and tuned to the same frequency. Filter coefficients are shared between the two CDMA DDC channels within a block.
VARIABLE
ddc_duc_ena
cdma_mode
Table 5. Programming
DESCRIPTION
When set turns on the DDC. When cleared the clock to the DDC is
stopped reducing its power consumption to essentially zero.
When set, puts the DDC block in dual CDMA2000 mode.
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