ISL5216_05 Datasheet, PDF (13/65 Pages) Intersil Corporation – Four-Channel Programmable Digital DownConverter

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 filter compute engine, a
FIFO/timer for evenly spacing samples (important when
implementing interpolation filters 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 filter compute engine. There are two
other inputs to the filter compute engine, they are a data
recirculation path for cascading filters and a magnitude and
dφ/dt feedback path for AM and FM filtering. There are seven
outputs from each back end processing section. These are I
and Q directly out of the filter compute engine (I2, Q2), I and
13
Q passed through the FIFO and AGC multipliers (I1, Q1),
magnitude (MAG), phase (or dφ/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 filter
compute engine. The routing information is embedded in the
instruction bit fields used to define the digital filter being
implemented in the filter compute engine.
July 8, 2005