Lpc2000

If my user application is running with interrupts occurring, then I 
need to disable all interrupts for a bit of time:

1) Should I use the C command "VICIntEnable=0x00000000"?
OR
2) Set the IRQ and FIQ bits in the cpsr?  Also, then do I have to be
in 
non-user mode (i.e. privileged mode) to enable/disable the IRQ/FIQ
bits 
in the cpsr?

At 07:30 PM 5/2/05 +0000, kaiandxiulpc2000 wrote:
>If my user application is running with interrupts occurring, then I
>need to disable all interrupts for a bit of time:
>
>1) Should I use the C command "VICIntEnable=0x00000000"?
>OR
>2) Set the IRQ and FIQ bits in the cpsr?  Also, then do I have to be
>in
>non-user mode (i.e. privileged mode) to enable/disable the IRQ/FIQ
>bits
>in the cpsr?

In my opinion number 2 will cause you the least problems.  In fact I would 
disable interrupts before modifying VICIntEnable. And yes you have to be in 
a mode other than user mode.  On the other hand there is no reason to be in 
user mode anyway.  The only thing that distinguishes user mode from system 
mode is that in user mode is that in user mode you cannot set and clear the 
interrupt enable bits.

Personally I prefer a disable/restore interrupt pair rather than a 
disable/enable interrupt pair.  There is an implementation of the former in 
the newlib-lpc library that should be easily separable from that library if 
desired.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> 
wrote:
> At 07:30 PM 5/2/05 +0000, kaiandxiulpc2000 wrote:
> >If my user application is running with interrupts occurring, then I
> >need to disable all interrupts for a bit of time:
> >
> >1) Should I use the C command "VICIntEnable=0x00000000"?
> >OR
> >2) Set the IRQ and FIQ bits in the cpsr?  Also, then do I have to 
be
> >in
> >non-user mode (i.e. privileged mode) to enable/disable the IRQ/FIQ
> >bits
> >in the cpsr?
> 
> In my opinion number 2 will cause you the least problems.  In fact I 
would 
> disable interrupts before modifying VICIntEnable. And yes you have 
to be in 
> a mode other than user mode.  On the other hand there is no reason 
to be in 
> user mode anyway.  The only thing that distinguishes user mode from 
system 
> mode is that in user mode is that in user mode you cannot set and 
clear the 
> interrupt enable bits.

Agree. Look back for postings on spurious interrupts. Fiddling with 
the VIC is not enough.


> 
> Personally I prefer a disable/restore interrupt pair rather than a 
> disable/enable interrupt pair.  There is an implementation of the 
former in 
> the newlib-lpc library that should be easily separable from that 
library if 
> desired.

Agree again.

restoring allows you to restore the previous state (ie. you should not 
always blindly turn interrupts on). Restoring allows you to use the 
same code in an interrupt or normal context etc.

I use two funtions  intGetDisable() and intEnable()

  int intval; // previous interrupt value

  intval = intGetDisable(); // Is the interrupt enabled? Disable if it 
is enabled;
  // protected code

  if(intval) 
      intEnable();