dspic asm sample codes

 ******************************************************************************


        .equ __33FJ256GP710, 1
        .include "p33FJ256GP710.inc"

;..............................................................................
;Configuration bits: We will use the MPLAB menu to configure the bits
;..............................................................................

;..............................................................................
;Program Specific Constants (literals used in code)
;..............................................................................

        .equ SAMPLES, 64         ;Number of samples


;..............................................................................
;Global Declarations:
;..............................................................................

        .global _wreg_init       ;Provide global scope to _wreg_init routine
                                 ;In order to call this routine from a C file,
                                 ;place "wreg_init" in an "extern" declaration
                                 ;in the C file.

        .global __reset          ;The label for the first line of code. 

        .global __T1Interrupt    ;Declare Timer 1 ISR name global



;..............................................................................
;Constants stored in Program space
;..............................................................................

        .section .myconstbuffer, code
        .palign 2                ;Align next word stored in Program space to an
                                 ;address that is a multiple of 2
ps_coeff:
        .hword   0x0002, 0x0003, 0x0005, 0x000A




;..............................................................................
;Uninitialized variables in X-space in data memory
;..............................................................................

         .section .xbss, bss, xmemory
x_input: .space 2*SAMPLES        ;Allocating space (in bytes) to variable.


;..............................................................................
;Uninitialized variables in Y-space in data memory
;..............................................................................

          .section .ybss, bss, ymemory
y_input:  .space 2*SAMPLES



;..............................................................................
;Uninitialized variables in Near data memory (Lower 8Kb of RAM)
;..............................................................................

          .section .nbss, bss, near
var1:     .space 2               ;Example of allocating 1 word of space for
                                 ;variable "var1".



;..............................................................................
;Code Section in Program Memory
;..............................................................................

.text                             ;Start of Code section
__reset:
; First initialize the stack pointer and the Stack pointer limit
        MOV #__SP_init, W15       ;Initalize the Stack Pointer
        MOV #__SPLIM_init, W0     ;Initialize the Stack Pointer Limit Register
        MOV W0, SPLIM
        NOP                       ;Add NOP to follow SPLIM initialization
        
;Next write code to setup the FRC clock to be divided by 256
;7.37 Mhz is thus reduced to 14.3Khz or Tcy = 70 us.  
		bset	CLKDIV,#10
		bset	CLKDIV,#9
		bset 	CLKDIV,#8

;********************************************************************************
;Next we set PORT A to be a output port
		bclr		TRISA,#0
;********************************************************************************
; Then light up the LED connected to PORTA bit 0

Again:
		bset 	PORTA,#0
; Add the delay for 0.5 seconds
		repeat 	#7142
		nop
		bclr 	PORTA,#0
		repeat	#7142
		nop
		bra		Again

; Add code to turn off the LED connected to PORTA bit 0


; Copy code written above to delay for 0.5 seconds


; write code to Repeat Loop

done:
        BRA     done              ;Place holder for last line of executed code


;..............................................................................
;Timer 1 Interrupt Service Routine
;Example context save/restore in the ISR performed using PUSH.D/POP.D
;instruction. The instruction pushes two words W4 and W5 on to the stack on
;entry into ISR and pops the two words back into W4 and W5 on exit from the ISR
;..............................................................................

__T1Interrupt:
        PUSH.D W4                  ;Save context using double-word PUSH

        ;<<insert more user code here>>

        BCLR IFS0, #T1IF           ;Clear the Timer1 Interrupt flag Status
                                   ;bit.

        POP.D W4                   ;Retrieve context POP-ping from Stack
        RETFIE                     ;Return from Interrupt Service routine



;--------End of All Code Sections ---------------------------------------------

.end                               ;End of program code in this file