;*****************************************************************************
;   MSP-FET430x110 Demo  - Software SPI Interface to HC595 Shift Register
;
;   Description: Transfer byte data in Data (R4) serially to HC595 and
;   latch data using RCLK. Data in incremented in the mainloop, effectively
;   incrementing HC595 QA - QH outputs.
;   ACLK = n/a, MCLK = SMCLK = default DCO ~800k
;
;                MSP430F1121     ^      HC595
;             -----------------  |  ----------
;            |                 | |-|/SRCLK    |  8
;            |             P2.2|-->|RCLK    Qx|--\->
;            |             P2.1|-->|SER       |
;            |             P2.0|-->|SRCLK  /OE|--|
;            |                 |   |          |  V
;
#define     Data     R4
RCLK        EQU      004h                   ; P2.2 Data Out
SER         EQU      002h                   ; P2.1 Data Out
SRCLK       EQU      001h                   ; P2.0 Serial Clock
;
;   M. Buccini
;   Texas Instruments Inc.
;   Feb 2005
;   Built with IAR Embedded Workbench Version: 3.21A
;*****************************************************************************
#include  <msp430x11x1.h>
;-----------------------------------------------------------------------------
            ORG     0F000h                  ; Program Start
;-----------------------------------------------------------------------------
RESET       mov.w   #0300h,SP               ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop Watchdog Timer
SetupP2     bic.b   #SRCLK+SER+RCLK,&P2OUT  ; Reset Clock, data and latch
            bis.b   #SRCLK+SER+RCLK,&P2DIR  ; Clock, data and latch as output
            mov.b   #0FFh,Data              ;
                                            ;
Mainloop    inc.b   Data                    ; Increment data to be transfered
            call    #TX_HC595               ; Data --> HC595
            call    #Delay                  ; Wait
            jmp     Mainloop                ; Repeat
                                            ;
;-----------------------------------------------------------------------------
TX_HC595;   Shift data from Data (R4) --> HC595.
;-----------------------------------------------------------------------------
            push.b  Data                    ; Save Data - TOS
            push.b  #08                     ; 8 bits to TX - TOS
TX_loop     bic.b   #SER,&P2OUT             ; SER reset
            rla.b   Data                    ; Data MSB -> Carry
            jnc     Clk_1                   ;
Out_1       bis.b   #SER,&P2OUT             ; SER set
Clk_1       bis.b   #SRCLK,&P2OUT           ; SRCLK set
Clk_0       bic.b   #SRCLK,&P2OUT           ; SRCLK reset
            dec.b   0(SP)                   ; All 8 bits sent?
            jnz     TX_loop                 ;
Latch_1     bis.b   #RCLK,&P2OUT            ; Latch data out
Latch_0     bic.b   #RCLK,&P2OUT            ;
            incd.w  SP                      ; bit counter off stack
            pop.b   Data                    ; Original data
            ret                             ; Return from subroutine
                                            ;
;-----------------------------------------------------------------------------
Delay;      Software delay
;-----------------------------------------------------------------------------
            push.w  #0FFFFh                 ; Delay to TOS
L1          dec.w   0(SP)                   ; Decrement TOS
            jnz     L1                      ; Delay over?
            incd.w  SP                      ; Clean TOS
            ret                             ;
                                            ;
;-----------------------------------------------------------------------------
;           Interrupt Vectors
;-----------------------------------------------------------------------------
            ORG     0FFFEh                  ; MSP430 RESET Vector
            DW      RESET                   ;
            END