LTC1285_15 Datasheet, PDF (21/24 Pages) Linear Technology – 3V Micropower Sampling 12-Bit A/D Converters in SO-8 Packages

LTC1285/LTC1288
TYPICAL APPLICATIONS N
Timing Diagram for Interface to the MC68HC11
CS
CLK
D_IN
SGL/
START
DIFF
ODD/
SIGN
MSBF
DON'T CARE
D_OUT
B11 B10 B9 B8
B7
B6 B5 B4 B3 B2 B1 B0
MPU
TRANSMIT
WORD
MPU
RECEIVED
WORD
0
0
0
0
0
0
0
1
BYTE 1
??
?
??
?
?
?
BYTE 1
SGL/
DIFF
ODD/
SIGN
MSBF
X
X
X
X
X
BYTE 2
?
?
?
0 B11 B10 B9 B8
BYTE 2
X
X
XX
XX
XX
BYTE 3 (DUMMY)
B7 B6 B5 B4 B3 B2 B1 B0
BYTE 3
LTC1285/88 • TA03
Hardware and Software Interface to the MC68HC11
DOUT FROM LTC1298 STORED IN MC68HC11 RAM
MSB
#62 0 0
0
0 B11 B10 B9 B8 BYTE 1
ANALOG
LSB
INPUTS
#63 B7 B6 B5 B4 B3 B2 B1 B0 BYTE 2
CH0
CS
CLK
LTC1288
D_OUT
CH1
D_IN
D0
SCK
MC68HC11
MISO
MOSI
LTC1285/88 • TA04
LABEL MNEMONIC
LDAA
STAA
LDAA
STAA
LDAA
STAA
LDAA
STAA
LDAA
STAA
LDX
LOOP
BCLR
LDAA
STAA
LDAA
OPERAND
#$50
$1028
#$1B
$1009
#$01
$50
#$A0
$51
#$00
$52
#$1000
$08,X,#$01
$50
$102A
$1029
COMMENTS
CONFIGURATION DATA FOR SPCR
LOAD DATA INTO SPCR ($1028)
CONFIG. DATA FOR PORT D DDR
LOAD DATA INTO PORT D DDR
LOAD DIN WORD INTO ACC A
LOAD DIN DATA INTO $50
LOAD DIN WORD INTO ACC A
LOAD DIN DATA INTO $51
LOAD DUMMY DIN WORD INTO
ACC A
LOAD DUMMY DIN DATA INTO $52
LOAD INDEX REGISTER X WITH
$1000
D0 GOES LOW (CS GOES LOW)
LOAD DIN INTO ACC A FROM $50
LOAD DIN INTO SPI, START SCK
CHECK SPI STATUS REG
LABEL MNEMONIC
WAIT1 BPL
LDAA
STAA
WAIT2 LDAA
BPL
LDAA
STAA
LDAA
STAA
WAIT3 LDAA
BPL
BSET
LDAA
STAA
JMP
OPERAND
WAIT1
$51
$102A
$1029
WAIT2
$102A
$62
$52
$102A
$1029
WAIT3
$08,X#$01
$102A
$63
LOOP
COMMENTS
CHECK IF TRANSFER IS DONE
LOAD DIN INTO ACC A FROM $51
LOAD DIN INTO SPI, START SCK
CHECK SPI STATUS REG
CHECK IF TRANSFER IS DONE
LOAD LTC1288 MSBs INTO ACC A
STORE MSBs IN $62
LOAD DUMMY INTO ACC A
FROM $52
LOAD DUMMY DIN INTO SPI,
START SCK
CHECK SPI STATUS REG
CHECK IF TRANSFER IS DONE
DO GOES HIGH (CS GOES HIGH)
LOAD LTC1288 LSBs IN ACC
STORE LSBs IN $63
START NEXT CONVERSION
21