Bootloader

Interrupt Vector

Interrupt vector on the C8051F320 is always at offset 0 in FLASH. Unfortunately, once bootloader wants to run a program, this means that we cannot re-target it from bootloader interrupt vector into the program interrupt vector. Instead, we have to re-target each interrupt separately.

The following code shows how it's done in DSerial bootloader.

<cpp> void R_uartInterrupt() __interrupt (4) _naked { _asm mov a, _IrqVector ; compare IrqVector to 0 jnz 00001$ mov a, (_IrqVector+1) jz 00002$ 00001$: ; if not 0, then we need to jump to it mov dpl, _IrqVector mov dph, (_IrqVector+1) mov a, #0x23 ; this is the offset for uart irq jmp @a+dptr 00002$: ; if it's 0, then we'll handle the irq lcall _uartInterrupt ; call our own interrupt handler reti _endasm; }

// repeat for the other irqs </cpp>

IrqVector is a global variable that is set to the location of interrupt vector before enabling interrupts.

<cpp> __data __at (0x7e) unsigned int IrqVector;

void main() { // ... IrqVector = 0x0800; EA = 1; // Global interrupt enable // ... } </cpp>