Xycom XVME-400, Manual

Page: 31 / 83

XVME-400/40l/490/491 Manual
October, 1989
3.3 MODULE INTERRUPT SOURCES
There are twelve sources of interrupts on the XVME-400/401/490/491 (three sources from
each serial channel). When enabled, each of these sources can generate VMEbus interrupts
on the level specified by jumpers JAI-JA3. The interrupt sources are prioritized during
the VMEbus IACK cycle, as shown in Table 3-2.
Table 3-2. Priority of Local Interrupt Sources
Channel Interrupt Source
0
Receive Character Available
0 Transmit Buffer Empty
0
External/Status Change
1 Receive Character Available
1 Transmit Buffer Empty
1 External/Status Change
2
Receive Character Available
2 Transmit Buffer Empty
2 External/Status Change
3
Receive Character Available
3
Transmit Buffer Empty
3 External/Status Change
Priority
Highest
Lowest
When the module responds to a VMEbus IACK cycle, the IACK vector is acquired from
the appropriate SCC chip and driven onto the VMEbus. Since each SCC can produce 8
vectors, SCC IACK vector register (WR2) must be initialized before interrupts are enabled.
When programmed to include status in the IACK vector (WR9:DO=l), the status high/low
bit (WR9:D4) determines whether IACK vector bits 3,2,1 or bits 4,5,6 will contain status
information. The status information returned in IACK vector is shown in Table 3-3 on
the following page:
3-3