AD7845SQ/883B Analog Devices, AD7845SQ/883B Datasheet - Page 10

• Manufacturer Part Number: AD7845SQ/883B
• Description: LC2MOS Complete 12-Bit Multiplying DAC
• Manufacturer: Analog Devices

AD7845
MICROPROCESSOR INTERFACING
16-BIT MICROPROCESSOR SYSTEMS
Figures 19, 20 and 21 show how the AD7845 interfaces to
three popular 16-bit microprocessor systems. These are the
MC68000, 8086 and the TM32010. The AD7845 is treated as
a memory-mapped peripheral to the processors. In each case, a
write instruction loads the AD7845 with the appropriate data.
The particular instructions used are as follows:
MC68000:
8086:
TMS32010: OUT
Figure 19. AD7845 to MC68000 Interface
Figure 20. AD7845 to 8086 Interface
Figure 21. TMS32010
MOVE
MOV
–10–
8-BIT MICROPROCESSOR SYSTEMS
Figure 22 shows an interface circuit for the AD7845 to the
8085A 8-bit microprocessor. The software routine to load data
to the device is given in Table IV. Note that the transfer of the
12 bits of data requires two write operations. The first of these
loads the 4 MSBs into the 7475 latch. The second write opera-
tion loads the 8 LSBs plus the 4 MSBs (which are held by the
latch) into the DAC.
2000 LOAD DAC: LXI
Table IV. Subroutine Listing for Figure 22
Figure 22. 8085A Interface
MVI
MOV
INR
MVI
MOV
RET
H,#3000
A,#“MS” Load the 4 MSBs of
M,A
L
A,#“LS”
M,A
The H,L register pair
are loaded with latch
address 3000.
data into accumulator.
Transfer data from
accumulator to latch.
Increment H,L pair to
AD7845 address.
Load the 8 LSBs of
data into accumulator.
Transfer data from
accumulator to DAC.
End of routine.
REV. B