boot_23xx.armasm

	/* ARM code to run user code */
	/* on the LPC23xx chips, the bootloader defaults to using the RC */
	/* osciallator and it activates the PLL to create 14.78 MHz, even */
	/* if there is no crystal.  However, when we use try to jump to */
	/* the user's code, their startup routine may (incorrectly) assume */
	/* the PLL is not enabled and crash if it is.  So in addition to */
	/* remapping the reset vector to flash, we have to shut off the */
	/* PLL so the user's startup code sees the same conditions as it */
	/* would following a hard reset */
begin:
	adr	r0, const
	ldr	r1, [r0]	/* r1 points to MEMMAP register */
	ldr	r2, [r0,#4]	/* r2 points to PLLCON */
	ldr	r3, [r0,#8]	/* r3 points to PLLFEED */
	mov	r0, #1
	str	r0, [r1]	/* remap interrupt vectors to flash */
	mov	r4, #0xAA
	mov	r5, #0x55
	str	r0, [r2]	/* disconnect the PLL, PLLCON = 1 */
	str	r4, [r3]
	str	r5, [r3]
	mov	r0, #0
	str	r0, [r2]	/* disable the PLL, PLLCON = 0 */
	str	r4, [r3]
	str	r5, [r3]
	mov	pc, #0		/* and then jump to the user's code */
const:
	.int	0xE01FC040	/* MEMMAP register */
	.int	0xE01FC080	/* PLLCON */
	.int	0xE01FC08C	/* PLLFEED */