MP7645B 데이터 시트보기 (PDF) - Exar Corporation

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MP7645B

CMOS Buffered Multiplying 12-Bit Digital-to-Analog Converter

Exar Corporation 

WRITE CYCLE TIMING DIAGRAM

CS

WR

DATA IN

(DB0-DB11)

MP7645B

tCS

tCH

tWR

tDH

tDS

VIH

VIL

DATA VALID

VDD

0

VDD

0

VDD

0

APPLICATION NOTES

Refer to Section 8 for Applications Information

MICROPROCESSOR INTERFACING OF THE

MP7645B

The MP7645B can interface directly to both 8- and 16-bit mi-

croprocessors via its 12-bit wide data latch using standard CS

and WR control signals.

A typical interface circuit for an 8-bit processor is shown

(Figure 1.) This arrangement uses two memory addresses, one

for the lower 8 bits of data to the DAC and one for the upper 4 bits

of data into the DAC via the latch.

Figure 2. shows an alternative approach for use with 8-bit

processors which have a full 16-bit wide address bus such as

6800, 8080 and Z80. This technique uses the 12 lower address

lines of the processor addresses bus to supply data to the DAC,

thus each MP7645B connected in this way uses 4k bytes of ad-

dress locations. Data is written to the DAC using a single mem-

ory write instruction. The address field of the instruction is or-

ganized so that the lower 12 bits contain the data for the DAC

and the upper 4 bits contain the address of the 4k block at which

the DAC resides.

A15

A0

CPU

WR

DB7

DB0

ADDRESS BUS

Q0

ADDRESS

DECODE

Q1

CS

LATCH

WR

CS

DB11

DB8

MP7645B

WR

DB7

DB0

8-BIT DATA BUS

Q0 DECODED ADDRESS FOR DAC

Q1 DECODED ADDRESS FOR LATCH

Figure 1. 8-Bit Processor to MP7645B Interface

A15

A0

CPU

WR

4

ADDRESS

DECODE

Q0

16-BIT ADDRESS BUS

DB11

12

DB0

CS MP7645B

WR

DB7

DATA BUS

DB0

Figure 2. Connecting the MP7645B to 8-Bit

Processors via the Address Bus

Rev. 2.00

5

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