; Definitions  -- references to 'UM' are to the User Manual.

; Timer Stuff -- UM, Table 173

T0  equ 0xE0004000      ; Timer 0 Base Address
T1  equ 0xE0008000

IR  equ 0           ; Add this to a timer's base address to get actual register address
TCR equ 4
MCR equ 0x14
MR0 equ 0x18

TimerCommandReset   equ 2
TimerCommandRun equ 1
TimerModeResetAndInterrupt  equ 3
TimerResetTimer0Interrupt   equ 1
TimerResetAllInterrupts equ 0xFF

; VIC Stuff -- UM, Table 41
VIC equ 0xFFFFF000      ; VIC Base Address
IntEnable   equ 0x10
VectAddr    equ 0x30
VectAddr0   equ 0x100
VectCtrl0   equ 0x200

Timer0ChannelNumber equ 4   ; UM, Table 63
Timer0Mask  equ 1<<Timer0ChannelNumber  ; UM, Table 63
IRQslot_en  equ 5       ; UM, Table 58

IO1DIR  EQU 0xE0028018
IO1SET  EQU 0xE0028014
IO1CLR  EQU 0xE002801C
IO1PIN  EQU 0xE0028010
IO0DIR EQU 0xE0028008
IO0SET EQU 0xE0028004
IO0CLR EQU 0xE002800C

    AREA    InitialisationAndMain, CODE, READONLY
    IMPORT  main

; (c) Mike Brady, 2014–2016.

    EXPORT  start
start
; |----------------------------|
; |----INITIALISTION CODE------|
; |----------------------------|

; Initialise the VIC
    ldr r0,=VIC         ; looking at you, VIC!
    ldr r1,=irqhan
    str r1,[r0,#VectAddr0]  ; associate our interrupt handler with Vectored Interrupt 0
    mov r1,#Timer0ChannelNumber+(1<<IRQslot_en)
    str r1,[r0,#VectCtrl0]  ; make Timer 0 interrupts the source of Vectored Interrupt 0
    mov r1,#Timer0Mask
    str r1,[r0,#IntEnable]  ; enable Timer 0 interrupts to be recognised by the VIC
    mov r1,#0
    str r1,[r0,#VectAddr]       ; remove any pending interrupt (may not be needed)
; Initialise Timer 0
    ldr r0,=T0          ; looking at you, Timer 0!
    mov r1,#TimerCommandReset
    str r1,[r0,#TCR]
    mov r1,#TimerResetAllInterrupts
    str r1,[r0,#IR]
    ldr r1,=(14745600/2)-1   ; 5 ms = 1/200 second
    str r1,[r0,#MR0]
    mov r1,#TimerModeResetAndInterrupt
    str r1,[r0,#MCR]
    mov r1,#TimerCommandRun
    str r1,[r0,#TCR]
;from here, initialisation is finished, so it should be the main body of the main program

; |----------------------------|
; |---INITIALISE SCHEDULER-----|
; |----------------------------|


    LDR lr,=programTwo
    LDR sp,=stackTwo
    STMFD sp!, {r0-r12, lr}
    LDR R1,=stackPointTwo
    STR sp, [R1]

    LDR R0,=programRunning
    MOV R1, #1
    STR R1, [R0]

    LDR sp,=stackOne

    B programOne



























; |----------------------------|
; |---------THREAD ONE---------|
; |----------------------------|


programOne

    ldr r1,=IO1DIR
    ldr r2,=0x000f0000  ;select P1.19--P1.16
    str r2,[r1]     ;make them outputs
    ldr r1,=IO1SET
    str r2,[r1]     ;set them to turn the LEDs off
    ldr r2,=IO1CLR
; r1 points to the SET register
; r2 points to the CLEAR register

    ldr r5,=0x00100000  ; end when the mask reaches this value
wloop   ldr r3,=0x00010000  ; start with P1.16.
floop   str r3,[r2]     ; clear the bit -> turn on the LED

;delay for about a half second
    ldr r4,=2000000
dloop   subs    r4,r4,#1
    bne dloop

    str r3,[r1]     ;set the bit -> turn off the LED
    mov r3,r3,lsl #1    ;shift up to next bit. P1.16 -> P1.17 etc.
    cmp r3,r5
    bne floop
    b   wloop


endProgramOne b endProgramOne




























; |----------------------------|
; |---------THREAD TWO---------|
; |----------------------------|


programTwo

    ldr r1,=IO1DIR
    ldr r2,=0x000f0000  ;select P1.19--P1.16
    str r2,[r1]     ;make them outputs
    ldr r1,=IO1SET
    str r2,[r1]     ;set them to turn the LEDs off
    ldr r2,=IO1CLR
; r1 points to the SET register
; r2 points to the CLEAR register

    ldr r5,=0x00100000  ; end when the mask reaches this value
wloop2  ldr r3,=0x00010000  ; start with P1.16.
floop2  str r3,[r2]     ; clear the bit -> turn on the LED

;delay for about a half second
    ldr r4,=200000
dloop2  subs    r4,r4,#1
    bne dloop2

    str r3,[r1]     ;set the bit -> turn off the LED
    mov r3,r3,lsl #1    ;shift up to next bit. P1.16 -> P1.17 etc.
    cmp r3,r5
    bne floop2
    b   wloop2



endProgramTwo b endProgramTwo



































; |----------------------------|
; |---------INTERRUPTS---------|
; |----------------------------|
    AREA    InterruptStuff, CODE, READONLY
irqhan  sub lr,lr,#4
    stmfd   sp!,{r0-r12, lr}    ; the lr will be restored to the pc

    LDR R0,=programRunning
    LDR R1, [R0]
    CMP R1, #1

    LDRNE R2,=stackPointTwo
    LDREQ R2,=stackPointOne
    STR sp, [R2]

    LDRNE R2,=stackPointOne
    LDREQ R2,=stackPointTwo
    LDR sp, [R2]

    EOR R1, #0x3
    STR R1, [R0]

;here you'd put the unique part of your interrupt handler
;all the other stuff is "housekeeping" to save registers and acknowledge interrupts
;this is where we stop the timer from making the interrupt request to the VIC
;i.e. we 'acknowledge' the interrupt
    ldr r0,=T0
    mov r1,#TimerResetTimer0Interrupt
    str r1,[r0,#IR]     ; remove MR0 interrupt request from timer
;here we stop the VIC from making the interrupt request to the CPU:
    ldr r0,=VIC
    mov r1,#0
    str r1,[r0,#VectAddr]   ; reset VIC

    ldmfd   sp!,{r0-r12, pc}^   ; return from interrupt, restoring pc from lr
                ; and also restoring the CPSR














; |----------------------------|
; |---------SUBROUTINE---------|
; |----------------------------|
    AREA    Subroutines, CODE, READONLY


































    AREA    Stuff, DATA, READWRITE
programRunning DCD 0
stackOne SPACE 1024
stackTwo SPACE 1024
stackPointOne DCD 0
stackPointTwo DCD 0

fireWorks DCD 0x1, 0x2, 0x4, 0x8

    END