Datasheet
AD7302
–12–
REV. 0
MICROPROCESSOR INTERFACING
AD7302–ADSP-2101/ADSP-2103 Interface
Figure 29 shows an interface between the AD7302 and the
ADSP-2101/ADSP-2103. The fast interface timing associated
with the AD7302 allows easy interface to the ADSP-2101/
ADSP-2103.
ADDR
DECODE
DATA BUS
ADDRESS BUS
CS
DB0
DB7
AD7302*
A/B
DMA0
DMA14
WR
EN
DMD0
DMD15
ADSP-2101*/
ADSP-2103*
WR
DMS
A**
A+1**
**ADDITIONAL CIRCUITRY OMITTED FOR CLARITY.
**A DECODED ADDRESS FOR DAC A.
**A+1 DECODED ADDRESS FOR DAC B.
LDAC
Figure 29. AD7302–ADSP-2101/ADSP-2103 Interface
Two addresses are decoded to select loading data to either
DAC A or DAC B. LDAC is permanently tied low in this
circuit, so the selected DAC output is updated on the rising
edge of the WR signal.
Data is loaded to the AD7302 input register using the following
ADSP-21xx instruction:
DM (DAC) = MR0
MR0 = ADSP-21xx MR0 Register.
DAC = Decoded DAC Address.
AD7302–TMS32020 Interface
Figure 30 shows an interface between the AD7302 and the
TMS32020. The address decoder is used to decode the
addresses for DAC A and DAC B. Data is loaded to the
AD7302 using the following instruction:
OUT DAC, D
DAC = Decoded DAC Address.
D = Data Memory Address.
ADDR
DECODE
DATA BUS
ADDRESS BUS
CS
DB0
DB7
AD7302*
A/B
A0
A15
STRB
EN
DMD0
DMD15
TMS32020
WR
IS
A**
A+1**
**ADDITIONAL CIRCUITRY OMITTED FOR CLARITY.
**A DECODED ADDRESS FOR DAC A.
**A+1 DECODED ADDRESS FOR DAC B.
LDAC
R/W
Figure 30. AD7302–TMS32020 Interface
In the circuit shown the LDAC is hardwired low, thus the
selected DAC output is updated on the rising edge of WR.
Some applications may require simultaneous updating of both
DACs in the AD7302. In this case the LDAC signal can be
driven from an external timer or can be controlled by the
microprocessor. One option for simultaneous updating is to
decode the LDAC from the address bus so that a write opera-
tion at this address will simultaneously update both DAC
outputs. A simple OR gate with one input driven from the
decoded address and the second input from the WR signal will
implement this function.
AD7302–8051/8088 Interface
Figure 31 shows a serial interface between the AD7302 and the
8051/8088 processors. The address decoder is used to decode
the addresses for DAC A and DAC B.
ADDR
DECODE
ADDRESS/DATA BUS
ADDRESS BUS
DB0
DB7
AD7302*
/B
A8
A15
AD0
AD7
8051/8088
OR
A**
A+1**
**ADDITIONAL CIRCUITRY OMITTED FOR CLARITY.
**A DECODED ADDRESS FOR DAC A.
**A+1 DECODED ADDRESS FOR DAC B.
ALE
OCTAL
LATCH
Figure 31. AD7302–8051//8088 Interface