??? 03/04/04 08:18 Read: times |
#65916 - RE: 16 ext. interrups sources Responding to: ???'s previous message |
8259's are useless with an 8051 type processor. If you really need many external interrupts do two things. Find a derivative type than can handle more than the standard two interrupts. Secondly you can use several small package type microcontrollers that can manage a number of the I/Os for the main processor.
Lastly, it is possible to build yourself a priority interrupt queueing logic block inside a CPLD. But forget using old hat 82xx chips. The 8259 chip in particular needs to be able to provide a vector byte during an interrupt acknowledge cycle IACK/. The 8051 has NO provision to generate IACK/ cycles. One could consider doing the IACK cycles in a software access to the chip but mapping the bus of the chip to XRAM data space makes such a scheme so inefficient since MOVX instructions need to be used that your interrupt support time gets excessively long. So bad that in general you would get better performance just polling the 16 inputs!!! There are other ways to gain additional interrupt inputs to an 8051 type part than just using the INT0 and INT1 pins. The available technigues will depend on the processor derivative that you select. Some have 8-bit wide port setup to accept inputs from a keyboard called a keyboard interrupt module. Others have analog comparator inputs that can be easily biased in such a way so as to be able to generate interrupts from a digital signal. It is possible to use the T2/T3/T4 pins in an input capture mode and generate a corresponding interrupt from these inputs. Lastly the typical PCA assembly on many parts has 5 timer pins that can be configured in one or two ways to generate an interrupt when the timer pins are used as a gate input or capture strobe. I would think that if you looked at a Cygnal C8051F020 type part in its 100 pin TQFP package it should just be possible to configure it to support external pins making interrupts as follows: Comparators - 2 Timers - 5 PCA Channels - 6 Ext Ints - 2 -------------- Pin Ints - 15 Michael Karas |
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16 ext. interrups sources | 01/01/70 00:00 | |
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