L2340
DEVICES INCORPORATED
Digital Synthesizer
FM, PM — Frequency Modulation,
Phase Modulation Control
OBIQ — Data Input/Output Format
Select
OEQ — y-coordinate Data Output
Enable
FM and PM is the 2-bit Frequency
Modulation/Phase Modulation
Control that determines one of the
four modes shown in Table 2. When
full-scale is exceeded, the accumulator
will roll over correctly allowing
continuous phase accumulation
through 2π radians.
When OBIQ is HIGH, offset binary
format is selected. When OBIQ is
LOW, unsigned format is selected.
When OEQ is LOW, Q15-0 is enabled
for data output. When OEQ is HIGH,
Q15-0 is placed in a high-impedance
state.
OEI — x-coordinate Data Output
Enable
When OEI is LOW, I15-0 is enabled for
data output. When OEI is HIGH, I15-0
is placed in a high-impedance state.
FIGURE 1A. INPUT FORMATS
AM
PH
(RTP = 0)
Integer Unsigned Magnitude
14 13 12
214 213 212
Fract. Unsigned Mag./Two's Comp.
2
1
0
31 30 29
*±20 2–1 2–2
2
1
0
22 21 20
2–29 2–30 2–31
*±20 denotes two's complement sign or highest magnitude bit. Since phase angles are modulo 2π
and phase accumulator is modulo 232, this bit may be regarded as ±π
.
FIGURE 1B. OUTPUT FORMATS
I
Q
Integer Unsigned Magnitude (OBIQ = 0)
14 13 12
214 213 212
2
1
0
14 13 12
214 213 212
2
1
0
22 21 20
22 21 20
Offset Binary (OBIQ = 1)
15 14 13
NS 214 213
2
1
0
15 14 13
NS 214 213
2
1
0
22 21 20
22 21 20
NS denotes negative sign. (i.e. '1' negates the number)
Special Arithmetic Functions
08/16/2000–LDS.2340-E
3
LOGIC [ LOGIC DEVICES INCORPORATED ]
