LTC1197CS8 datasheet(23/28 Pages) LINER

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LTC1197/LTC1197L

LTC1199/LTC1199L

APPLICATI

TYPICAL

Interfacing to the Parallel Port of the

Intel 8051 Family

The Intel 8051 has been chosen to demonstrate the

interface between the LTC1199 and parallel port micro-

processors. Normally the CS, CLK and DIN signals would

be generated on three port lines and the DOUT signal read

on a fourth port line. This works very well. However, we

will demonstrate here an interface with the DIN and DOUT

of the LTC1199 tied together as described in the

SERIAL INTERFACE section. This saves one wire.

The 8051 first sends the start bit and MUX address to the

LTC1199 over the data line connected to P1.2. Then P1.2

is reconfigured as an input (by writing to it a one) and

the 8051 reads back the 8-bit A/D result over the same

data line.

LABEL

MNEMONIC

OPERAND

COMMENTS

MOV

A, #FFH

DIN word for LTC1199

SETB

P1.4

Make sure CS is high

CLR

P1.4

CS goes low

MOV

R4, #04

Load counter

LOOP 1

RLC

Rotate DIN bit into Carry

CLR

P1.3

CLK goes low

MOV

P1.2, C

Output DIN bit into Carry

SETB

P1.3

CLK goes high

DJNZ

R4, LOOP 1

Next bit

MOV

P1, #04

Bit 2 becomes an input

CLR

P1.3

CLK goes low

MOV

R4, #0AH

Load counter

LOOP

MOV

C, P1.2

Read data bit into Carry

RLC

Rotate data bit into ACC

SETB

P1.3

CLK goes high

CLR

P1.3

CLK goes low

DJNZ

R4, LOOP

Next bit

MOV

R2, A

Store MSBs in R2

MOV

C, P1.2

Read data bit into Carry

SETB

P1.3

CLK goes high

CLR

P1.3

CLK goes low

CLR

Clear ACC

RLC

Rotate data bit from Carry to

ACC

MOV

C, P1.2

Read data bit into Carry

RRC

Rotate right into ACC

RRC

Rotate right into ACC

MOV

R3, A

Store LSBs in R3

SETB

P1.4

CS goes high

CLK

DOUT

DIN

LTC1199

ANALOG

INPUTS

P1.4

P1.3

P1.2

8051

MUX ADDRESS

A/D RESULT

1197/99 TA06

DOUT from LTC1199 Stored in 8051 RAM

CLK

DATA (DIN/DOUT)

START

ODD/

SIGN

DUMMY

LTC1199 SENDS A/D RESULT

BACK TO 8051 P1.2

8051 P1.2 OUTPUTS DATA

TO LTC1199

8051 P1.2 RECONFIGURED

AS AN INPUT AFTER THE 4TH RISING

CLK AND BEFORE THE 4TH FALLING CLK

LTC1199 TAKES CONTROL OF DATA LINE

ON 4TH FALLING CLK

SGL/

DIFF

1197/99 TA08

1197/99 TA07

MSB

LSB

LTC1197CS8 Datasheet(PDF) 23 Page - Linear Technology

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