Vector Graphic Bitstreamer II, User Manual

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1.10
Interrupt vectors
and
priority
We have explained above that interrupts can be generated from any
combination of the three 8251 RxRDY lines, the three 8251 TxRDY lines, and
the 55 Hz real-time clock. You can use any of the 8080 or 280 interrupt
modes. If the mode you are using requires hardware to place a byte on the
data bus, you have a choice of nine different bytes, as shown in Table 10 in
Section 2.7. You specify the byte by installing jumpers in pads provided,
as described in Section 2.7.
The same byte is generated no matter what the interrupt source on the
board. However, if there are more than one aitstreamer II Boards in the
system, each of them can be wired to generate a different byte. Therefore,
software can determine which board is the source of the interrupt, but it
must poll the potential sources
wi
thin that board to determine Ythich one is
the actual source. Alternately, you can wire all the boards to put the saQe
byte on the data bus, and have software poll all the boards to find the
source of the interrupt.
If you would like to build more sophisticated interrupt handling or
priori tizing circuitry, the interrupt signals from the Bitstreamer II Board
can be passed to such a custom board over the 5-100 VI lines. Pads are
provided, as des~ribed in Section 2.7.