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;  
;******************************************************************************
;  This program creates a sinewave at the output of the DAC7513 D/A 
;   
;   P2.0, P2.1 and P1.7 as control signals for DAC7513
;  on Microtrend Sys. Inc. MS-3003 platform
;    Notice that there are two ways to modify sinewave frequency
;     1. Modify the software delay constant 
;     2. modify the value written into SCFQCTL 
;******************************************************************************
#include          "msp430x43x.h" ; Standard Equations
SYN   equ 0080h
SCLK  equ 001h
DIN   equ 002h
#define value R6
#define steps R7
           ; RSEG UDATA0
            RSEG CSTACK
            DS 0
            RSEG CODE
RESET       mov  #SFE(CSTACK),SP               ; Initialize stackpointer
StopWDT     mov     #WDTPW+WDTHOLD,&WDTCTL ; Stop watchdog

         ;mov.b  #SELM_DCO,&FLL_CTL1;  the CPU runs on DCO with these 
          ; 3 instructions
          ;bis.b #DCOPLUS,&FLL_CTL0;comment them out if you want regular 1.048Mhz
          ;mov.b #100,&SCFQCTL      
                  
               
           ; D/A DAC7513  control pins assigned to  P2.1 P2.0 and P1.7
           
            bic.b #BIT7,&CAPD       ;P1.7 
            bis.b #BIT0,&P2DIR      ; P2.0 direction output
            bis.b #BIT1,&P2DIR      ;P2.1  direction output
            bic.b #BIT7,&P1SEL      ;p1.7 OUTPUT  SELECT PORT NO COMPARATOR
            bis.b #BIT7,&P1DIR      ;p1.7 DIRECTION output
            bis.b #SYN,&P1OUT       ;p1.7  MAKE A ONE HERE initially on sync pin
            
            bic.b #BIT0,&P2OUT      ; P2.0 direction output
            bic.b #BIT1,&P2OUT      ;P2.1  direction output
            
                                            
SetupADC12  mov     #REFON+REF2_5V,&ADC12CTL0 ; 
 
  ;we only need the 2.5V reference and the REFon
              mov #00010h,steps     ; 16 steps 
              mov #0,R8   ;R8 is a pointer to sinewave table   
again         mov sinewave_table(R8),value
              call #sample 
              call #Delay   ;   go to sample output routine
              inc R8    ;       double increment for a word address
              inc R8
              cmp #0020h,R8  ; are we done with 32 increments ?
              jnz again      ; is one period over ?
              mov #0,R8
              jmp again   ;  yes,start again ,do another period           
sample;                    this routine simulates an SPI interface
              
                mov #0010h,steps         ; 16 steps 
beta            nop
                nop
                bic.b #SYN,&P1OUT        ;p1.7 OUTPUT MAKE A ONE HERE               
alfa            rlc value
                jc shift_a_one
shift_a_zero     bis.b #SCLK,&P2OUT                       
                bic.b #DIN,&P2OUT        ;P2.0 OUTPUT clear
                bic.b #SCLK,&P2OUT       ;P2.1 OUTPUT             
                jmp next             
shift_a_one     bis.b #SCLK,&P2OUT                       
                bis.b #DIN,&P2OUT        ;P2.0 OUTPUT  set
                bic.b #SCLK,&P2OUT       ;P2.1 OUTPUT               
next            dec steps
                jnz alfa
                mov #0010h,steps     ; 16 steps 
                bis.b #SYN,&P1OUT                       
                ret
              
sinewave_table  dw 0x0000          
                dw 0x009a
                dw 0x0256          
                dw 0x04ef             
                dw 0x7ff          
                dw 0x0b0e
                dw 0x0da7          
                dw 0x0f63
                dw 0x0fff          
                dw 0x0f63
                dw 0x0da7          
                dw 0x0b0e
                dw 0x07ff          
                dw 0x04ef
                dw 0x0256          
                dw 0x009a
              
              
Delay; Software delay
              push  #011fh
Dl1           dec.w 0(SP)
              jnz Dl1
              incd SP
              ret              
             ;
                                        
;------------------------------------------------------------------------------ 
;           Interrupt Vectors        
;------------------------------------------------------------------------------
            COMMON INTVEC
           ORG     RESET_VECTOR           ; MSP430 RESET Vector
RESET_VEC  DW     RESET                   ;
            END