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.

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