SIS Documentation
SIS3800
Scaler/Counter
Page 19 of 39
9 VME
Interrupts
Three VME interrupt sources are implemented in the SIS3800 firmware design:
•
Overflow
•
External Latch Shadow Input
•
Test Interrupt
The interrupter is of type D8(O).
The interrupt logic is shown below. For VME interrupt generation the corresponding interrupt
source has to be enabled by setting the respective bit in the VME control register (disabling is
done with the sources J/K bit). Interrupt generation has to be enabled by setting bit 11 in the
IRQ and version register. The internal VME interrupt flag can be used to check on an IRQ
condition without actually making use of interrupts on the bus.
The VME interrupt level (1-7) are defined by bits 8 through 10 and the VME interrupt vector
(0-255) by bits 0 through 7 of the VME IRQ and version register.
In general an interrupt condition is cleared by disabling the corresponding interrupt, clearing
the interrupt condition (i.e. clear overflow) and enabling the IRQ again.
Note: In most cases your experiment may not require interrupt driven scaler readout,
but the interrupt capability of the SIS3800 provides a way to overcome the problem of
missing front panel inputs on most commercial VME CPUs.
AND
Enable 2
Test
AND
Enable 1
ext. Shadow
AND
Enable 0
Overflow
OR
AND
VME IRQ
VME_IRQ_ENABLE
INTERNAL_VME_IRQ
Source 2
Source 1
Source 0
Clear
CtrlReg
Bit1
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
