Analog-to-Digital Converter

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Analog-to-Digital Converter

• Chapter 9
• MC9S12DP256

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Method of Successive Approximation
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Implementing Successive Approximation
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\ 9S12DP256 Analog-to-Digital Converter --
File ATD256.WHP HEX   0082 CONSTANT
ATD0CTL2 \ ATD Control Register 2 0084
CONSTANT ATD0CTL4 \ ATD Control
Register 4 0085 CONSTANT ATD0CTL5
\ ATD Control Register 5 0086 CONSTANT
ATD0STAT \ ATD Status Register 0090
CONSTANT ADR00H \ A/D Result
Register 0 ADCONV.ON ( -- ) 85
ATD0CTL4 C! \ 8-bit resol, /8 clock C0
ATD0CTL2 C! \ Set ADPU and AFFC  
ADCONV.OFF ( -- ) 0 ATDCTL2 C! \
Clear ADPU   WAIT.FOR.CONV ( -- ) BEGIN
7 ATD0STAT ?HI UNTIL
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  AVG4 ( -- n ) \ Average 4
values in ADR0 - ADR3 0 ADR00H 2- 4 FOR
\ sum addr DUP R_at_ 2 C_at_ \
sum addr val ROT SWAP \ sum addr
NEXT DROP 4 /   ADCONV ( ch --
val ) \ Avg 4 readings from channel ch
ADCONV.ON 8 MOD 80 OR ATDCTL5 C! \ ch lt 8
SCAN0 MULT0 WAIT.FOR.CONV AVG4 ADCONV.OFF
 
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  GET.4VALUES ( -- val4 val3 val2 val1 ) \
read 4 a/d regs ADR0H 2- 4 FOR
\ addr1 DUP R_at_ 2 C_at_ SWAP
\ valn addr1 NEXT DROP   ADCONV03
( -- val3 val2 val1 val0 ) \ Convert 1st 4
channels ADCONV.ON 10 ATDCTL5 C!
WAIT.FOR.CONV GET.4VALUES   ADCONV47
( -- val3 val2 val1 val0 ) \ Convert 2nd 4
channels ADCONV.ON 14 ATDCTL5 C!
WAIT.FOR.CONV GET.4VALUES   DECIMAL