Rainbow Electronics MX7535 - Manual (Page 13)

Z80 with MX7534/MX7535
Figure 12a is an interface circuit for the Z80, using the
MX7535. This is an example of an 8-bit processor inter-
face for these DACs. Figure 12b shows the schematic
for the MX7534.
MC6809 with MX7534
Figure 13a shows an interface circuit that enables the
MX7534 to be programmed using the MC6809 8-bit
microprocessor. Use the 16-bit D accumulator to simplify
data transfer. The two key processor instructions are:
LDD Load D accumulator from memory
STD Store D accumulator to memory
MC6502 with MX7534
Figure 13b shows an interface diagram for the MC6502
using the MX7534.
________________Digital Feedthrough
In the interface diagrams shown in Figures 9–13, the
digital inputs of the DAC are directly connected to the
microprocessor bus. Even when the device is not
selected, activity on the bus can feed through on the
DAC output through package capacitance and appear
as noise. To minimize noise, isolate the DACs from the
digital bus, as shown in Figures 14a and 14b.
MX7534/MX7535
Microprocessor-Compatible,
14-Bit DACs
______________________________________________________________________________________ 13
ASSUME DS:DACLOAD,CS:DACLOAD
DACLOAD SEGMENT AT 000
00
02
04
07
0B
0E 8CC9
8ED9
BF00D0
C705“YZWX”
EA0000
00FF MOV CX,CS
MOVDS,CX
MOVDI,#D000
MOV MEM,#YZWX :DEFINE DATA SEGMENT REGISTER EQUAL
:TO CODE SEGMENT REGISTER
:LOAD DI WITH D000
:DAC LOADED WITH WXYZ
:CONTROL IS RETURNED TO THE MONITOR PROGRAM
ASSUME DS:DACLOAD,CS:DACLOAD
DACLOAD SEGMENT AT 000
00
02
04
07
0A
0B
0C
0F
10
11
14 8CC9
8ED9
BF02D0
C605“MS”
47
47
C605“LS”
47
47
C60500
EA0000 MOV CX,CS
MOVDS,CX
MOVDI.#D002
MOV MEM,#“MS”
INC DI
INC DI
MOV MEM,#“LS”
INC DI
INC DI
MOV MEM,#00
JMP MEM :DEFINE DATA SEGMENT REGISTER EQUAL
:TO CODE SEGMENT REGISTER
:LOAD DI WITH D002
:DAC LOADED WITH “MS”
:LS INPUT REGISTER LOADED WITH “LS”
:CONTENT OF INPUT REGISTERS ARE LOADED TO THE DAC REGISTER
:CONTROL IS RETURNED TO THE MONITOR PROGRAM
Table 6a. Sample Program for Loading the MX7535
Table 6b. Sample Program for Loading the MX7534 from 8086
2000
01
02
03
04
05
06
07
08
09
0A
0B
0C
200D 26
30
2E
01
3E
“MS”
77
2C
3E
“LS”
77
2C
77
CF MVIH,#30
MVIL,#01
MVIA,#“MS”
MOV M,A
INR L
MVI A#“LS”
MOV M,A
INR L
MOV M,A
RST I
Table 6c. Sample Program for Loading
the MX7534 from 8085A