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???
04/11/05 12:51
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 		 #91366 - !EA/Vpp
Responding to: ???'s previous message
To program from external memory, you need !EA to be low to read from external memory and Vpp to be high to program. Since this is the same pin you obviouly need it in two states.

Some clever mean might be devised were it not for the fact that this state is latched to the falling edge of reset.

Erik

List of 34 messages in thread
TopicAuthorDate
Philips p89c51RDx Programmer project            01/01/70 00:00      
   Useful Project            01/01/70 00:00      
   Useful Project. Count me in            01/01/70 00:00      
      lets try something....            01/01/70 00:00      
         No Go            01/01/70 00:00      
            see my "other things.."            01/01/70 00:00      
               bootrom code            01/01/70 00:00      
                  Jan, please email me at .....            01/01/70 00:00      
                  BootRom Code            01/01/70 00:00      
                     Boot ROM address range            01/01/70 00:00      
                        2kb boot code            01/01/70 00:00      
                           B oot from External Memory            01/01/70 00:00      
                              !EA/Vpp            01/01/70 00:00      
   why not the simple solution: NoTouch            01/01/70 00:00      
      Too Late            01/01/70 00:00      
         Try this, it has worked for some            01/01/70 00:00      
   Philips's angwer            01/01/70 00:00      
      the most often changed            01/01/70 00:00      
      an RX2 'fix' from the horse's mouth...            01/01/70 00:00      
         neat            01/01/70 00:00      
         Nice!            01/01/70 00:00      
            I'll look tomorrow...            01/01/70 00:00      
               I take it back            01/01/70 00:00      
                  you're NOT as stupid as you think.......            01/01/70 00:00      
         Not possible !!!            01/01/70 00:00      
            respectfully disagree...            01/01/70 00:00      
               Re: respectfully disagree...            01/01/70 00:00      
                  I didcussed it above earlier today...            01/01/70 00:00      
               difference Philips.vs.Atmel            01/01/70 00:00      
                  other things...            01/01/70 00:00      
                     lets make the ckt even simpler...            01/01/70 00:00      
                     maybe ?            01/01/70 00:00      
                        using the EA pin            01/01/70 00:00      
               which bits            01/01/70 00:00      

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