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From: bc338569@longs.LANCE.ColoState.Edu (Brian Catlin)
Newsgroups: comp.sys.ibm.pc.hardware,sci.electronics
Subject: getting more interrupts
Message-ID: <14137@ccncsu.ColoState.EDU>
Date: 10 Apr 91 22:43:36 GMT
Sender: news@ccncsu.ColoState.EDU
Reply-To: bc338569@longs.LANCE.ColoState.Edu.UUCP (Brian Catlin)
Distribution: na
Organization: Engineering College, Colorado State U.  Ft. Collins, CO  80523
Lines: 41


HI,

I would like to know if any of you could help me to add more IRQ levels to
my computer.  I have a Tandy 1400LT with a NEC V20 CPU and a NEC uPD71059
interrupt control unit.  I have thought of the following diagram as a
possible solution.  These 71059's can be cascaded but an initialization
word must be changed and I have no idea how to do that.

Well, here is the very rough drawing:

     |--------|                                     |-----------|
     |        |                                     |           |
     |uPD71059|  |----------------------------|     | NEC V20   |
     |        |  |      \----\                |     |           |
     |     INT|--+-------\ OR \___|-----------------|INT        |
     |        |      |---/    /               |     |           |
     |        |      |  /----/      /----|    |     |           |
     |   INTAK|-----------------|__/ AND |-------+--|INTAK      |
     |        |      |             \     |----|  |  |           |
     |--------|      |              \----|       |  |-----------|
                     |                           |
                     |              /----|       |
     |--------|      |          ___/ AND |-------|
     |        |      |          |  \     |----| 
     |uPD71059|      |          |   \----|    | 
     |        |      |          |             | 
     |     INT|------+------------------------|
     |        |                 |
     |   INTAK|-----------------|   
     |        |    
     |--------|


If anyone has any other ideas I would greatly appreciate them.

Thanks,

B. J. Catlin

bc338569@longs.lance.colostate.edu