/*
* Script that SHOULD generate an interrupt using the AIC,
* but WHY doesn't it?
* For at91sam7x256 ( olimex sam7-ex256 )
*/

.set AIC_BASE, 0xFFFFf000
@interrupt enable command
.set AIC_IVR,  0x0100
.set AIC_FVR,  0x0104
.set AIC_IMR,  0x0110
.set AIC_CISR, 0x0114
.set AIC_SMR3, 0x000C
.set AIC_SVR3, 0x008C

.set AIC_IECR, 0x0120
.set AIC_ICCR, 0x0128
.set AIC_ISCR, 0x012C
.set AIC_EOICR,0x0130
.set AIC_FFER, 0x0140

.set PIO_B_BASE, 0xFFFFf600
@ PIO enable/disable/status registers
.set PIO_PER, 0x0000
.set PIO_PDR, 0x0004
.set PIO_PSR, 0x0008
@ Output enable/disable/status registers
.set PIO_OER, 0x0010
.set PIO_ODR, 0x0014
.set PIO_OSR, 0x0018
@ Set/clear/status of output data
.set PIO_SODR, 0x0030
.set PIO_CODR, 0x0034
.set PIO_ODSR, 0x0038
@ Pin data status
.set PIO_PDSR, 0x003C
@ Interrupt enable
.set PIO_IER,  0x0040


.global _vec_reset

/* Initial vector table */
_vec_reset: b _init_reset
_vec_undef: b _irq_handler
_vec_swi: b _irq_handler
_vec_pabt: b _irq_handler
_vec_dabt: b _irq_handler
_vec_rsv: b _irq_handler
_vec_irq: b _irq_handler
_vec_fiq: b _irq_handler


_init_reset:
@ 1. Enable interrupts from peripheral 3 on AIC
ldr r0, =AIC_BASE
@ 1.1 Set Mode
ldr r1, =0x67 @ Mode will be: Positive edge triggered, Priority 7 (max)
str r1, [r0, #+AIC_SMR3]
@ 1.2 Enable interrupts on PID3
ldr r1, =(1<<3)
str r1, [r0, #+AIC_IECR]

@ 2. Enable interrupts of all kinds in current processor mode (default is supervisor mode after reset)
cpsie afi

@ 3.A Simulate an interrupt from peripheral 3
str r1, [r0, #+AIC_ISCR]
@ 3.B Do a software interrupt instead if you wish to confirm that [4.B] works
@ swi 69

@ 4.A Loop endlessly (should not be reached)
spin: b spin

@ 4.B IRQ Handler: Blink the connected LED endlessly
_irq_handler:
@ 4.B.1 Enable PIO output on PB21
ldr r0, =PIO_B_BASE
ldr r1, =(1<<21)
str r1, [r0, #+PIO_PER]
str r1, [r0, #+PIO_CODR]
str r1, [r0, #+PIO_OER]
@ 4.B.2 Strobe the LED endlessly
strobe_loop:
bl delay
str r1, [r0, #+PIO_SODR] @ high
bl delay
str r1, [r0, #+PIO_CODR] @ low
b strobe_loop

@ X. "delay" subroutine
delay:
ldr r3, =1000
delay_loop:
add r3, r3, #-1
cmp r3, #0
movle pc, r14 @ return from bl
b delay_loop