23

LTC1283

S

APPLICATI

TYPICAL

MNEMONIC

DESCRIPTION

LDA

#$50

CONFIGURATION DATA FOR SPCR

STA

$0A

LOAD CONFIGURATION DATA INTO $0A

LDA

#$FF

CONFIGURATION DATA FOR PORT C DDR

STA

$06

LOAD CONFIGURATION DATA INTO PORT

C DDR

BSET 0, $02

MAKE SURE CS IS HIGH

JSR

READ –/+

DUMMY READ CONFIGURES LTC1283 FOR

NEXT READ

JSR

READ +/–

READ CH6 WITH RESPECT TO CH7

JSR

READ –/+

READ CH7 WITH RESPECT TO CH6

JSR

CHK SIGN DETERMINES WHICH READING HAS VALID

DATA, CONVERTS TO 2’s COMPLEMENT

AND STORES IN RAM

READ – / +: LDA

#$3F

JSR

TRANSFER READ LTC1283 ROUTINE

LDA

$60

LOAD MSBs FROM LTC1283 INTO ACC

STA

$71

STORE MSBs IN $71

LDA

$61

LOAD LSBs FROM LTC1283 INTO ACC

STA

$72

STORE LSBs IN $72

RTS

RETURN

Read + / –: LDA

#$7F

JSR

TRANSFER READ LTC1283 ROUTINE

LDA

$60

LOAD MSBs FROM LTC1283 INTO ACC

STA

$73

STORE MSBs IN $73

LDA

$61

LOAD LSBs FROM LTC1283 INTO ACC

STA

$74

STORE LSBs IN $74

RTS

RETURN

TRANSFER: BCLR 0, $02

CS GOES LOW

STA

$0C

LOOP 1:

TST

$0B

TEST STATUS OF SPIF

BPL

LOOP 1

LOOP TO PREVIOUS INSTRUCTION IF NOT

DONE

LDA

$0C

LOAD CONTENTS OF SPI DATA REG. INTO

ACC

STA

$0C

START NEXT CYCLE

STA

$60

STORE MSBs IN $60

MNEMONIC

DESCRIPTION

LOOP 2:

TST

$0B

TEST STATUS OF SPIF

BPL

LOOP 2

LOOP TO PREVIOUS INSTRUCTION IF NOT

DONE

BSET 0, $02

CS GOES HIGH

LDA

$0C

LOAD CONTENTS OF SPI DATA REG. INTO

ACC

STA

$61

STORE LSBs IN $61

RTS

RETURN

CHK SIGN: LDA

$73

LOAD MSBs OF +/– READ INTO ACC

ORA

$74

OR ACC (MSBs) WITH LSBs OF +/– read

BEQ

MINUS

IF RESULT IS 0 GOTO MINUS

CLC

CLEAR CARRY

ROR $73

ROTATE RIGHT $73 THROUGH CARRY

ROR $74

ROTATE RIGHT $74 THROUGH CARRY

LDA

$73

LOAD MSBs OF +/– READ INTO ACC

STA

$77

STORE MSBs IN RAM LOCATION $77

LDA

$74

LOAD LSBs OF +/– READ INTO ACC

STA

$87

STORE LSBs IN RAM LOCATION $87

BRA

END

GOTO END OF ROUTINE

MINUS:

CLC

CLEAR CARRY

ROR $71

SHIFT MSBs OF –/+ READ RIGHT

ROR $72

SHIFT LSBs –/+ READ RIGHT

COM $71

1’s COMPLEMENT OF MSBs

COM $72

1’s COMPLEMENT OF LSBs

LDA

$72

LOAD LSBs INTO ACC

ADD

#$01

ADD 1 TO LSBs

STA

$72

STORE ACC IN $72

CLRA

CLEAR ACC

ADC

$71

ADD WITH CARRY TO MSBs. RESULT IN

ACC

STA

$71

STORE ACC IN $71

STA

$77

STORE MSBs IN RAM LOCATION $77

LDA

$72

LOAD LSBs IN ACC

STA

$87

STORE LSBs IN RAM LOCATION $87

END:

RTS

RETURN

Sneak-A-Bit Code for the LTC1283 Using the MC68HC05C4

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of circuits as described herein will not infringe on existing patent rights.