Motorola HC08 interrupts

The '08 core has a table of interrupt vectors in the memory map. You need to populate these vectors correctly so that the 2-byte addresses point to the interrupt service routines.

Interrupts are largely a hardware thing. The hardware fetches the associated vector.

The name of the interrupt service routine, with most development tools, is irrelevant. You could name it "my_dog_fido" and it would be OK, so long as the name of the routine matched the name used to populate the interrupt vector.

However, with most development tools (and you should have let us know which tools you're using), you would want to give the function a special qualifier (typically "interrupt" or "_interrupt_" or "@interrupt") to the compiler know it is compiling an ISR. This affects the termination sequence (RTI versus RTS), as well as rules about how to use and restore certain registers and memory areas.

Dave.

Hi Dave,

Thanks for the reply. Like I said, I'm new to this and unfortunately I have no idea how to populate this "Interrupt Vector" that you talk about. I know what you mean by it I just don't know how to populate it.

I'm using CodeWarrior to write the code and download them to my chip.

Thanks in advance, Aria

Look at the examples supplied with CodeWarrior, like the demo M68QTY demo board software.

The vector table for the QY is found on the datasheet. Please refer to page 32 of the datasheet (Rev. 5) found here:

To populate the interrupt vector table for the interrupts you are want to use (you don't have to populate them all unless you are willing to use them) in Codewarrior you simply define an interrupt service routine (and populate its vector table entry at the same time) as the following:

interrupt NN void YourInterruptNameHere (void) { }

Where NN is the vector table entry.

0 for Reset (NEVER CHANGE THIS UNLESS YOU PROVIDE YOUR OWN STARTUP FILE) 1 for the Software Interrupt 2 for the external IRQ 3 Not used 4 Timer Channel 0 ... 15 Keyboard Interrupt 16 ADC

Example:

interrupt 15 void MyFirstKeyboardInterrupt (void) { KBSCR |= 0x04; /* Ack this interrupt */ /* Do your stuff here */ }

void main (void) { KBIER |= 0x5; /* Enable KBI0 and KBI2 IRQs */ EnableInterrupts; /* main loop goes here */ }

To simply test your Interrupt handing you can use the simulator and write a handler to populate and process the Software Interrupt. Here is the example;

interrupt 1 void MySoftwareInterrupt (void) { __asm ( "nop" ); /* Place your breakpoint here */ }

void main (void) { EnableInterrupts; __asm ( "swi" ); /* Perform a sowftare interrupt */ for (;;); }

Happy coding!

Hi,

Thanks for the helpful post. Just one thing is unclear now:

You say "Where NN is the vector table entry". Are you talkinga bout the vector table on page 32 of the manual? because in that one it says that IF15 is the ADC vector so i figure the ADC interrupt should be 15 but this is obviously not the case. So, what vector table are we talking about and how do i access it to see what number is what?

Thanks, Aria

The vector table for the QY is found on the datasheet. Please refer to page 32 of the datasheet (Rev. 5) found here:

To populate the interrupt vector table for the interrupts you are want to use (you don't have to populate them all unless you are willing to use them) in Codewarrior you simply define an interrupt service routine (and populate its vector table entry at the same time) as the following:

interrupt NN void YourInterruptNameHere (void) { }

Where NN is the vector table entry.

0 for Reset (NEVER CHANGE THIS UNLESS YOU PROVIDE YOUR OWN STARTUP FILE) 1 for the Software Interrupt 2 for the external IRQ 3 Not used 4 Timer Channel 0 ... 15 Keyboard Interrupt 16 ADC

Example:

interrupt 15 void MyFirstKeyboardInterrupt (void) { KBSCR |= 0x04; /* Ack this interrupt */ /* Do your stuff here */ }

void main (void) { KBIER |= 0x5; /* Enable KBI0 and KBI2 IRQs */ EnableInterrupts; /* main loop goes here */ }

To simply test your Interrupt handing you can use the simulator and write a handler to populate and process the Software Interrupt. Here is the example;

interrupt 1 void MySoftwareInterrupt (void) { __asm ( "nop" ); /* Place your breakpoint here */ }

void main (void) { EnableInterrupts; __asm ( "swi" ); /* Perform a sowftare interrupt */ for (;;); }

Happy coding!

Hi,

Thanks for the response. It is very helpful. Only one thing remains unclear and I can't figure it out. You say where "NN is the number in the vector table." How are you reading this number? and where is this vector table? is it the one on page 32 of the datasheet? Because looking at that one, It says

so i figure 15 would be the interrupt for ADC, but obviously it's not so i guess i don't know how to read the table. Which table should I use to read these numbers and is there a special method to reading them? (sorry if this questions sounds too unprofessional but i'm just learning).

thx in advance, Aria

Yes, I know it sounds confusing. The vector table is basically a table of 16-bit addresses that the CPU indexes so it can know to which address "jump" when an interrupt happens. When an interrupt happens the CPU loads the contents of the vector table to its Program Counter register so it can start executing interrupt code.

When you say

$FFDE ADC conversion complete vector (high) $FFDF ADC conversion complete vector (low)

You are actually referring to the locations in flash memory on which the 16-bit address of the ADC Interrupt function can be found.

However an easier way to refer to these locations is by naming them by pair. So $FFDE and $FFDF is pair number 16. Why?

Because of the following:

FFFF:FFFE pair 0 - RESET

FFFD:FFFC pair 1 - SWI

FFFB:FFFA pair 2

And so on...

FFDF:FFDE is pair 16

Ignore what the Vector Column in Table 2-1 says. By naming IF1 through IF15 to vectors

pairs 2 through 16, the authors wanted to differentiate the interrupts that are usually related to hardware events and have NOTHING to do with the way Codewarrior defines interrupt vectors. The later defines interrupts vectors as pairs starting from 0. Simply count the rows from bottom up on TABLE 2-1 starting from 0 (reset) and that will give you the vector number NN for Codewarrior.

phew! thx a lot. you just brought an end to 4 days of searching for how they were numbering these interrupts. thx again.