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ISL5216 Datasheet, PDF (13/65 Pages) Intersil Corporation – Four-Channel Programmable Digital DownConverter | |||
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Back End Data Routing
PATH 0
FROM
CIC
(4:0)
M
FILTER
U
COMPUTE
X
ENGINE
ISL5216
AGC
LOOP
FILTER
PATH 1
MUX
FIFO/
TIMER
AGC
MULT
CART
TO
POLAR
PATH 2
PATH 3
MAG: I
dphi/dt: Q
I1
Q1
SHIFT
d/dt
GAIN
x1, x2
x4, x8
MAG
M
U
PHASE
X
I2
Q2
I2
Q2
DESTINATION BIT MAP
(BITS 28:18 OF FIR INSTRUCTIONS BIT FIELD)
EXT AGC
GAIN
28 27 26 25 24 23 22 21 20 19 18
28
27
26, 25
24
23
22:18
AGC LOOP GAIN SELECT (PATH 01 ONLY)
UPDATE AGC LOOP (PATH 01 ONLY)
PATH 00 - - IMMEDIATE FILTER PROCESSOR FEEDBACK PATH
01 - - FIFO/AGC PATH TO I1 AND Q1
10 - - DIRECT OUT/CASCADE PATH TO I2 AND Q2
11 - - FIFO/AGC PATH TO I2 AND Q2
STROBE OUTPUT SECTION (START SERIAL OUTPUT WITH THIS SAMPLE)
FEED MAG/PHASE BACK TO FILTER PROCESSOR
FILTER PROCESSOR SEQUENCE STEP NUMBER
Back End Section
One back-end processing section is provided per channel.
Each back end section consists of a ï¬lter compute engine, a
FIFO/timer for evenly spacing samples (important when
implementing interpolation ï¬lters and resamplers), an AGC
and a cartesian-to-polar coordinate conversion block. A
block diagram showing the major functional blocks and data
routing is shown above. The data input to the back end
section is through the ï¬lter compute engine. There are two
other inputs to the ï¬lter compute engine, they are a data
recirculation path for cascading ï¬lters and a magnitude and
dÏ/dt feedback path for AM and FM ï¬ltering. There are seven
outputs from each back end processing section. These are I
and Q directly out of the ï¬lter compute engine (I2, Q2), I and
13
Q passed through the FIFO and AGC multipliers (I1, Q1),
magnitude (MAG), phase (or dÏ/dt), and the AGC gain
control value (GAIN). The I2/Q2 outputs are used when
cascading back end stages. The routing of signals within the
back end processing section is controlled by the ï¬lter
compute engine. The routing information is embedded in the
instruction bit ï¬elds used to deï¬ne the digital ï¬lter being
implemented in the ï¬lter compute engine.
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