Re: [uCsimm] irq level 6 and higher

From: Tom Walsh (
Date: Wed Apr 18 2001 - 12:13:50 EDT

daniel haensse wrote:
> can anybody tell me what kind of kernel resources and driver use interrupts
> level 6 and higher on the ez328. According to the uP spec. its the timer, irq6
> and emuirq.
> I think Tom board use emuirq for its dallas rtc. Does anything use the timer?

Hi Dani,

The Timer is only used by the BSP_sched_init() in
arch/m68knommu/platform/68EZ328/config.c, also used by the
timer_interrupt() in arch/m68knommu/kernel/time.c. In order to use the
timer for general purpose, you must free it from the jiffies timebase, I
did this with an external counter.

I replaced the use of the internal timer with that of an external
periodic source due to the poor timekeeping of the 68EZ328 when on the
internal timer. By taking the 32kHz processor clock drive and dividing
it down, I got it to 128 HZ. I would not recommend attaching anything
to the crystal of the CPU, this is one reason I used the Dallas clock
chip, it has enough drive level to also drive a '393 counter.

To use something other than 100 HZ, you must edit include/asm/param.h to
set the HZ, be careful though, if you read the nesting of the #ifdef's,
you will discover that the #def for the CONFIG_UCSIMM is in conflict
with the CONFIG_MC68EZ328 #def. Add your new platform #def after the
existing ones and you should be fine.

When driving the EMUIRQ (level7) pin, you must hold it high (+3v) when
coming out of reset, or you will immediately enter the emulator mode.
HIZ must be pulled high or else you could tri-state the bus when coming
out of reset as well. I solved the problem of the EMUIRQ line by gating
the 128HZ periodic signal off and enabling it later (in config.c).



Tom Walsh - WN3L - Embedded Systems Consultant
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"Windows? No thanks, I have work to do..."
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