README

See the top level README file for more information on documentation
and how to run these programs.

Derived from blinker07, but instead of IRQ this uses FIQ

diff ../blinker07/vectors.s vectors.s

21,22c21,22
< irq_handler:        .word irq
< fiq_handler:        .word hang
---
> irq_handler:        .word hang
> fiq_handler:        .word irq

connect the handler to the fiq exception vector rather than the
irq exception vector


90c90
<     bic r0,r0,#0x80
---
>     bic r0,r0,#0x40

enable the fiq interrupt rather than irq interrupt

95c95
<     push {r0,r1,r2,r3,r4,r5,r6,r7,r8,r9,r10,r11,r12,lr}
---
>     push {r0,r1,r2,r3,r4,r5,r6,r7,lr}
97c97
<     pop  {r0,r1,r2,r3,r4,r5,r6,r7,r8,r9,r10,r11,r12,lr}
---
>     pop  {r0,r1,r2,r3,r4,r5,r6,r7,lr}

fiq mode has its own r8-r12 registers, making it that much faster to
get in and get out.


diff ../blinker07/blinker07.c blinker08.c
166c166,167
<     PUT32(0x2000B210,0x00000002);
---
>     PUT32(0x2000B210,0x00000000);
>     PUT32(0x2000B20C,0x80|1);

the BCM manual says to not enable the irq if using fiq.  The irq enable
was a bitmask for interrupts 0 to 31, the fiq wants the interrupt number
so 0x2 is bit number 1 so we want interrupt number 1. The bcm manual
says that bit 7 of the fiq enable register, enables the fiq interrupt,
0x80 is bit 7.