LTC1289 Linear Technology, LTC1289 Datasheet - Page 25

• Manufacturer Part Number: LTC1289
• Description: 3 Volt Single Chip 12-Bit Data Acquisition System
• Manufacturer: Linear Technology

READ – / + : LDA #$3F
TYPICAL
D
Location $77B12B11B10B9B8B7B6B5
Location $87B4B3B2B1B0filled with 0s
D
D
D
D
SNEAK-A-BIT Code for the LTC1289 Using the MC68HC05C4
OUT
IN
IN
IN
IN
100111111
201111111
300111111
words for LTC1289
from LTC1289 in MC68HC05C4 RAM
MNEMONIC
LDA #$50
STA $0A
LDA #$FF
STA $06
BSET 0, $02
JSR READ –/+
JSR READ +/–
JSR READ –/+
JSR CHK SIGN
JSR TRANSFER
LDA $60
STA $71
LDA $61
STA $72
RTS
(ODD/SIGN)
A
PPLICATI
Sign
MUX Addr.
SNEAK-A-BIT Code
Configuration data for SPCR
Load configuration data into $0A
Configuration data for port C DDR
Load configuration data into port C DDR
Make sure CS is high
Dummy read configures LTC1289 for
next read
Read CH6 with respect to CH7
Read CH7 with respect to CH6
Determines which reading has valid
data, converts to 2's complement and
stores in RAM
Load D
Read LTC1289 routine
Load MSBs from LTC1289 in ACC
Store MSBs in $71
Load LSBs from LTC1289 in ACC
Store LSBs in $72
Return
O
IN
UNI
word for LTC1289 into ACC
U
DESCRIPTION
LSB
MSBF
S
Length
Word
LTC1289 TA05
READ +/–:
TRANSFER: BCLR 0, $02
LOOP 1:
LOOP 2:
CHK SIGN: LDA $73
MINUS:
END:
SNEAK-A-BIT Code for the LTC1289 Using the MC68HC05C4
MNEMONIC
LDA #$7F
JSR TRANSFER
LDA $60
STA $73
LDA $61
STA $74
RTS
STA $0C
TST
BPL LOOP 1
LDA $0C
STA $0C
STA $60
TST
BPL LOOP 2
BSET 0, $02
LDA $0C
STA $61
RTS
ORA $74
BEQ MINUS
CLC
ROR $73
ROR $74
LDA $73
STA $77
LDA $74
STA $87
BRA END
CLC
ROR $71
ROR $72
COM $71
COM $72
LDA $72
ADD #$01
STA $72
CLRA
ADC $71
STA $71
STA $77
LDA $72
STA $87
RTS
$0B
$0B
Load D
Read LTC1289 routine
Load MSBs from LTC1289 into ACC
Store MSBs in $73
Load LSBs from LTC1289 into ACC
Store LSBs in $74
Return
CS goes low
Load D
Test status of SPIF
Loop to previous instruction if not done
Load contents of SPI data reg into ACC
Start next cycle
Store MSBs in $60
Test status of SPIF
Loop to previous instruction if not done
CS goes high
Load contents of SPI data reg into ACC
Store LSBs in $61
Return
Load MSBs of +/– read into ACC
Or ACC (MSBs) with LSBs of +/– read
If result is 0 goto minus
Clear carry
Rotate right $73 through carry
Rotate right $74 through carry
Load MSBs of +/– read into ACC
Store MSBs in RAM locations $77
Load LSBs of +/– read into ACC
Store LSBs in RAM location $87
Goto end of routine
Clear carry
Shift MSBs of –/+ read right
Shift LSBs of –/+ read right
1's complement of MSBs
1's complement of LSBs
Load LSBs into ACC
Add 1 to LSBs
Store ACC in $72
Clear ACC
Add with carry to MSBs. Result in ACC
Store ACC in $71
Store MSBs in RAM locations $77
Load LSBs in ACC
Store LSBs in RAM location $87
Return
IN
IN
word for LTC1289 into ACC
into SPI. Start transfer
DESCRIPTION
LTC1289
25