>    2. Problem getting started (Jim Peterson)
>I've got a problem I hope someone might help me with. I'm building an application using a 87C52 microcontroller.
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>  In the design I have tied the EA pin low so that all code memory is external. I've done this mostly because I don't have a programmer for the 87C52 but I do have a eprom programmer for a 27C256 device.
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>The problem I'm having is that the following simple program just does not run. I'm wondering if there is some additional software initialization need that I've overlooked. Of course I'm using the sdcc compiler and have been successful in writing code which I have downloaded to a develpoment board running the Paulmon2 software.
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>The code is simply intended to flash a LED which I have connected to an output pin of a 8255 io chip. Symptoms include the address lines are not functioning per the code, the RD pin appears inactive,and PSEN appears ok. I have both a eprom emulator and a eprom programmer tried both with similar results
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your code looks ok. did you try simulating it? how do you *know* that 27c256 is being read? i also suspect h/w problem. try ANDing PSEN and RD,

peter