Xycom XVME 200, Manual

Page: 32 / 57

XVME-200/290 Manual
December, 1987
3.3 MODULE VMEbus INTERRUPT CAPABILITY
Four sources of interrupts exist on the XVME-200 and the XVME-290. These are
the timer and port interrupt sources from both PI/T #l and PI/T #2.
When
enabled, each of the four interrupt sources can generate VMEbus interrupts on the
level selected by jumpers JAI-JA3 (refer to Section 2.4.3 of this manual). The four
local interrupt sources are prioritized during the VMEbus IACK cycle. Table 3-2
shows the priority of the four local interrupt sources.
Table 3-2. Priority of Local Interrupt Sources
PI/T #l Port Interrupt
Highest Priority
PI/T #2 Port Interrupt
PI/T #l Timer Interrupt
PI/T #2 Timer Interrupt Lowest Priority
When the module responds to a VMEbus IACK cycle, the IACK vector is acquired
from the corresponding PI/T vector register (refer to the 68230 Manual for location
and operation) and driven onto the VMEbus.
Each PI/T device produces 5 different
vectors, 4 from the ports and 1 from the timer.
Thus, ten different VMEbus IACK
vectors can be provided by the XVME-200 and XVME-290 Modules. The appropriate
PI/T IACK vector registers must be initialized before interrupts are enabled (refer
to 68230 Manual).
3.3.1
Module VMEbus Interrupt Enabling
As
mentioned in the previous section, the ports and timer of both PI/T devices have
the capability of generating VMEbus interrupts.
The following subsections explain
the general procedure for enabling the port and timer interrupts.
3.3.1.1
Port C/Alternate Function Initialization
Basically, the interrupt initialization procedures begin by programming the Port
C/Alternate function lines on the PI/T devices to carry the interrupt control
functions. The operation of the Port C/Alternate function lines is covered in depth
in the 68230 Manual, however, for the sake of clarity Figure 3-3 is included in this
manual.
F i g u r e 3 - 3 d e f i n e s t h e P o r t C / A l t e r n a t e f u n c t i o n l i n e s a n d their
programmed direction for primary module use.
Notice that some of the pins retain
the possibility of being used as Port C single-bit inputs/outputs if the module
interrupt and timer capabilities are not being used (i.e., pins 1 and 3), while others
must be dedicated to module control functions (i.e., pins 0 and 1 should always be
programmed as outputs to control the direction of the Port A and B data buffers,
and pins 4, 5, 6, and 7 are dedicated to timer and port interrupt control).
3-5