CCS Manual Problem..

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia

I am trying to work out how to specify a specific interrupt handler is high, fast and no clear.

PCH v3.243 (had wrong version listed)

I have #device high_ints = true specified

I expect it to be of the form:
#int_timer3 high, fast, noclear

but the compiler spits the dummy for the high "macro" at the #int_timer3 line. The compiler will not accept high anywhere on the #int_timer3 line.

The #int section of the manual refers the reader to the #device section for building the high priority handlers but it does not provide any information on it.

Can someone enlighten me?
_________________
Regards, Andrew

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Ttelmah · Guest

3.143, is _old_.
It predates the introduction of the '#device high_ints=true' command.
It only supports one 'high priority' keyword, 'fast'. You can spcify just _one_ interrupt as 'fast', and this wll then have the high priority control bit set. The compiler requires _you_ to do everything for this interrupt (it will not save the registers, and will not clear the interrupt for you).
Beware, that on most (all?) chips, if you specify any other interrupt as 'fast', the hardware will also make int_rb0 into a high priority interrupt, and if this interrupt is in use, you will need to add the code to work out which interrupt has occured, and call the required handler.

Best Wishes

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia

sorry typo - it was PCH 3.243
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

Ttelmah · Guest

OK.
You can only ever use 'one' of 'high', or 'fast' on an interrupt. 'high', triggers the interrupt to be set as high priority, but otherwise to be treated 'normally', with the compiler saving the registers, and clearing the flags. 'fast', also sets the interrupt as high priority, but uses 'retfie 1' on exit. To confuse things, 'high', will also use 'retfie 1', if it is not also in use elsewhere!...
On slightly older compilers, 'fast', would not save the registers (which the manual says), but on current versions, it behaves the same as 'high', including testing the interrupt flags.
Neither command supports 'noclear'....
At present, compiler support or using high priority interrupts, is _worse_ than it was a few versions ago. On older versions, you could just have used 'fast', and then saved the registers yourself, and cleared the interrupt flag yourself. On the current versions, the easiest (and safest...) way to use 'custom' high priority interrupt behaviour is to go completely DIY. Unfortunately, there is no equivalent to the 'int_global' command, for the high priority interrupt handler... Crying or Very sad

So, the easiest way to do what you want, would be to go 'back' to an older compiler, and just use the 'fast' keyword. Round about 3.191, allows this to work.
Sorry, this is an area that is very poor.

Best Wishes

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia

Bummer. No wonder I could not get this to work. It was the do it yourself method I use to use.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Ttelmah · Guest

Yes.
The problem is that on latter versions (not sure of the exact switch, but just below 3.200 somewhere), the behaviour of 'fast', was changed, making it nearly identical to 'high'. It therefore does all the register saving.
As an example, this is part of the listing from a 'fast' routine, which does it's own register saving, using 3.191: