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rgb-driver-01/main.S

189 lines
4.8 KiB
ArmAsm

.file "main.S"
#include <msp430g2553.h>
#define PC r0
#define SP r1
#define SR r2
;; --- register usage --------------------------------
;; r4: synchronization between main loop and isr
;; bit0 signals byte done from isr
;; r5: data byte to be handled by isr
;; r6: bit-counter, only used within isr
;; r7: screen data start/next pointer
;; r8: screen data end pointer
;; r9: next screen data byte, prepared in mainloop
#define SIGNAL_INIT_VALUE 0x00
#define SIGNAL_BYTE_DONE 0x01
#define SIGNAL_ISR_ENABLE 0x02
#define SIGNAL_REGISTER r4
#define DATA_BYTE_REGISTER r5
#define NEXT_DATA_BYTE_REGISTER r9
#define DATA_NEXT_ADDRESS_REGISTER r7
#define DATA_LAST_ADDRESS_REGISTER r8
#define BIT_COUNTER_REGISTER r6
#define BIT_COUNTER_INIT_VALUE 0x01
;; ---------------------------------------------------
.section ".rodata","a"
screendata:
.byte 0b00000001
.byte 0b00000011
.byte 0b00000111
.byte 0b00001111
screendataend:
.byte 0xff
red:
colors1:
.byte 0b01001111
colors2:
.byte 0b01000111
colors3:
.byte 0b01000011
.byte 0
blue:
.byte 0b11001111
.byte 0b11000111
.byte 0b11000011
.byte 0
green:
.byte 0b10001111
.byte 0b10000111
.byte 0b10000011
.byte 0
;; .text is the name of the section, it is a hint for the linker to
;; allocate the section
;; ax: a means allocatable by linker, x means executable
;; @progbits is a hint for the linker to allocate this section into
;; program memory (flash)
.section ".text","ax",@progbits
_start:
;; disable watchdog
mov.w #WDTPW|WDTHOLD, &WDTCTL
;; configure clock system to the highest frequency
mov.b #DCO0|DCO1|DCO2, &DCOCTL
mov.b #XT2OFF|RSEL0|RSEL1|RSEL2|RSEL3, &BCSCTL1
mov.b #0, &BCSCTL2
mov.b #0, &BCSCTL3
;; initialize stack pointer with value from linker
mov.w #__stack, SP
init:
;; configuration of GPIO Ports
mov.b #BIT0|BIT1|BIT2, &P1DIR
mov.b #BIT1|BIT4, &P2DIR
mov.b #BIT1|BIT4, &P2SEL
;; timer configuration
;; configure and stop timer
;; cycle time is 56.25ns
mov.w #ID_0|MC_0|TACLR|TASSEL_2, &TA1CTL
;; 2.0us
mov.w #45, &TA1CCR0
;; a bit less
mov.w #10, &TA1CCR1
mov.w #22, &TA1CCR2
;; configure output mode for TA0.1
mov.w #CCIE, &TA1CCTL0
mov.w #OUTMOD_7, &TA1CCTL1
mov.w #OUTMOD_7, &TA1CCTL2
;; initialize bit-counter for isr
mov.b #BIT_COUNTER_INIT_VALUE, BIT_COUNTER_REGISTER
;; initialize isr-sync register
mov.b #SIGNAL_INIT_VALUE, SIGNAL_REGISTER
;; screen data start/next into DATA_NEXT_ADDRESS_REGISTER
mov.w #screendata, DATA_NEXT_ADDRESS_REGISTER
;; screen data end into DATA_LAST_ADDRESS_REGISTER
mov.w #screendataend, DATA_LAST_ADDRESS_REGISTER
;; load first screen data value into DATA_BYTE_REGISTER
mov.b @DATA_NEXT_ADDRESS_REGISTER, DATA_BYTE_REGISTER
inc.w DATA_NEXT_ADDRESS_REGISTER
;; start timer in up mode
bis.w #MC0, &TA1CTL
;; enable interrupts
eint
mainloop:
;; prepare next byte to handle by isr
;; first, check whether we are already at the end of screen data
cmp.w DATA_NEXT_ADDRESS_REGISTER, DATA_LAST_ADDRESS_REGISTER
jnz mainloop_prepare_next_byte
;; in that case rollover to the start again
mov.w #screendata, DATA_NEXT_ADDRESS_REGISTER
mainloop_prepare_next_byte:
;; load the byte from the screen data next pointer
mov.b @DATA_NEXT_ADDRESS_REGISTER, NEXT_DATA_BYTE_REGISTER
;; and increase the pointer
inc.w DATA_NEXT_ADDRESS_REGISTER
mainloop_wait_for_isr:
;; check bit0 in sync register, wait for the signal from
;; the isr
bit #SIGNAL_BYTE_DONE, SIGNAL_REGISTER
jz mainloop_wait_for_isr
;; load data
mov.b NEXT_DATA_BYTE_REGISTER, DATA_BYTE_REGISTER
;; clear the signal
bic #SIGNAL_BYTE_DONE, SIGNAL_REGISTER
;; mark the cycle
bis #BIT2, &P1OUT
bic #BIT2, &P1OUT
;; continue
jmp mainloop
; --- timer isr ---
;; r6: exclusively used by isr as bit-counter
timer1_a0_isr:
;; func begin marker
bis #BIT0, &P1OUT
;; check isr idle bit
bit #SIGNAL_ISR_ENABLE, SIGNAL_REGISTER
jnz timer1_a0_isr_exit
;; shift msb of data register r5 into carry flag and set or reset P1.1 accordingly
rla.b DATA_BYTE_REGISTER
jnc timer1_a0_isr_false_bit
bis #BIT1, &P1OUT
jmp timer1_a0_isr_end
timer1_a0_isr_false_bit:
bic #BIT1, &P1OUT
;; shift bit-counter, after eight shifts signal byte done and reset bit-counter
timer1_a0_isr_end:
rla.b BIT_COUNTER_REGISTER
jnc timer1_a0_isr_exit
;; reset bit-counter
mov.b #BIT_COUNTER_INIT_VALUE, BIT_COUNTER_REGISTER
;; signal byte done
bis #SIGNAL_BYTE_DONE, SIGNAL_REGISTER
timer1_a0_isr_exit:
;; func end marker
bic #BIT0, &P1OUT
reti
;; .resetvec comes from linker
.section ".resetvec","ax",@progbits
.word _start
.end