TMC2330A
PRODUCT SPECIFICATION
Table 3a. X-Dimensional Marginal Overflows
TC
0
0
1
1
YPIN
0000 = 0
8000 =
π
0000 = 0
8000 =
π
OV
1
1
1
0
RXOUT
0000 = +0
8000 = -0
8000 = -32768
8000 = -32768
CORRECT X
+32768
-32768
+32768
-32768
Performing Scan Conversion with
the TMC2330A
Medical Imaging Systems such as Ultrasound, MRI, and
PET, and phased array Radar and Sonar systems generate
radial-format coordinates (range or distance, and bearing)
which must be converted into raster-scan format for further
processing and display. Utilizing the TMC2302A Image
Resampling Sequencer, a minimum chipcount Scan Con-
verter can be implemented which utilizes the trigonometric
translation performed by the TMC2330A to backwards-map
from a Cartesian coordinate set into the Polar source image
buffer address space.
As shown in Figure 2, the TMC2330A transforms the Carte-
sian source image addresses from the TMC2302A directly to
vector distance and angle coordinates, while the TMC2302A
writes the resulting resampled pixel values into the target
memory in raster fashion. Note that the ability to perform
this spatial transformation in either direction gives the user
the freedom to process images in either coordinate space,
with little restriction. Image manipulation such as zooms or
tilts can easily be included in the transformation by program-
ming the desired image manipulation into the TMC2302A’s
transformation parameter registers.
In all cases, RTP=0 (Polar-To-Rectangular mode) and
XRIN=8000 (incoming radius=32768).
Table 3b. Maximal Overflow (Radius In=65535)
TC
0
0
1
1
YPIN
0000 = 0
8000 =
π
0000 = 0
8000 =
π
OV
1
1
1
1
RXOUT
7FFF = +32767
FFFF = -32767
FFFF = -1
0001 = +1
CORRECT X
+65535
-65535
+65535
-65535
In all cases, RTP=0 (Polar-To-Rectangular mode) and
XRIN=7FFF (incoming radius=65535, which will always
overflow).
Numeric Underflow
In RTP=1 (Rectangular-To-Polar) mode, if XRIN=YPIN=0, the
angle is undefined. Under these conditions, the TMC2330A
will output the expected radius of 0 (RXOUT= 0000) and an
angle of 1.744 radians (PYOUT=4707). This angle is an artifact
of the CORDIC algorithm and is not flagged as an error,
since the angle of any 0 length vector is arbitrary.
π/2
65535
X = R (Cos
θ)
Y = R (Sin
θ)
and
R=
X2 + Y2
θ
= Tan-1 (Y/X)
If R
≤
32767, overflow will not occur (Region A).
If R > 32767, overflow will not occur (Region B) if |X|
≤
32767 and |Y|
≤
32767.
If R > 32767, overflow will occur (Region C) if |X|
≥
32768 or |Y|
≥
32768.
C
32767
B
A
R
Y
θ
X
32767
65535
Figure 1. First Quadrant Coordinate Relationships
REV. 1.1.8 10/31/00
11
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