atdpro1.asm

hc12dg128a的AD转换程序

;* Title:  ATD.ASM                                                    *
;*         "Analog to Digital Converter (Using the A/D Converter)"    *
;* Description:                                                       *
;* ------------                                                       *
;*  This program makes it first to utilize the ATD on the  
;*  HC12 to measure a POTENTIOMETER signal output routed from the     *
;*  outside worknet to the HC12 ATD pins .                               
;*  First the ATDCTL Registers are initialized. A delay loop of 100   *
;*  usec is then executed. The resolution is set up followed by a     *
;*  conversion set up on channel. After waiting for the status bit    *
;*  to set, the result goes to the D accumulator and then goes to the *
;*  data code.
  INCLUDE 'EQUATES.ASM'      ;Equates for all registers user Variables
; and bit Equates

; ----------------------------------------------------------------------
;           ATD PROGRAM
; ----------------------------------------------------------------------
     XDEF ATDPRO,ATD0,ATD1,ATD2,ATD3,ATD4,ATD5,ATD6,ATD7
ATDDATA: SECTION
ATD0: DS.W 1
ATD1: DS.W 1
ATD2: DS.W 1
ATD3: DS.W 1
ATD4: DS.W 1
ATD5: DS.W 1
ATD6: DS.W 1
ATD7: DS.W 1
ATDCODE: SECTION       
ATDPRO:
        LDS     #$3FFF          ; Set the stack point
        BSR     INIT            ; Branch to INIT subroutine to Initialize ATD
        BSR     CONVERT         ; Branch to CONVERT Subroutine for conversion
DONE:   BRA     DONE                   ; Branch to Self, Convenient place for breakpoint

; ----------------------------------------------
;           Subroutine INIT: Initialize ATD    ;
; ----------------------------------------------

INIT:   
        LDAA    #$90            ; Allow ATD to function normally,
        STAA    ATD0CTL2         ; ATD Flags clear normally & disable interrupts
        BSR     DELAY           ; Delay (100 uS) for WAIT delay time.
        LDAA    #$00            ; Select continue conversion in BGND Mode
        STAA    ATD0CTL3         ; Ignore FREEZE in ATDCTL3
        LDAA    #$C1            ; Select Final Sample time = 2 A/D clocks
        STAA    ATD0CTL4         ; Prescaler = Div by 4 (PRS4:0 = 1)
        RTS                     ; Return from subroutine

; ----------------------------------------------
;              Subroutine CONVERT:             
; ----------------------------------------------
;  Set-up ATD, make multiple conversion and store 
;  the result to a memory location.
;  Configure and start A/D conversion
CONVERT:LDAA    #$70            ; Initializes ATD S8C=1,SCAN=1,MULT=1, PAD6, Write Clears Flag
	STAA    ATD0CTL5            ; 8 conversions on a MUTIPLE Conversion sequence, 
WTCONV: BRCLR   ATD0STAT0,#$80,WTCONV ; Wait for Sequence Complete Flag
    LDD ADR00
    STD ATD0
    LDD ADR01
    STD ATD1
    LDD ADR02
    STD ATD2
    LDD ADR03
    STD ATD3
    LDD ADR04
    STD ATD4
    LDD ADR05
    STD ATD5
    LDD ADR06
    STD ATD6
    LDD ADR07
    STD ATD7             ; Loads conversion result into Accumulator               
	                     ; and then loads them into the datacode
    RTS                  ; Return from subroutine
; -------------------------------
;    Subroutine DELAY 100 uS    
; -------------------------------
; Delay Required for ATD converter to Stabilize (100 uSec)
DELAY:
	LDAA    #$C8            ; Load Accumulator with "100 uSec delay value"
SUBDELAY:  DECA             ; Decrement ACC
	BNE    SUBDELAY         ; Branch if not equal to Zero
    RTS                     ; Return from subroutine