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???
06/12/07 13:36
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#140588 - TxD pulled down for ISP. Clever!
Responding to: ???'s previous message
while your solution is fine, I'd still leave a backdoor (C)Erik Malund, tied to TxD pin being pulled down upon startup.


Actually, I was thinking about a pin used as a backdoor but I didn't come up with such a smart idea.

Basically, if I short-circuit TxD (P3.1 = 0xB1) to RS232 ground, uP enters programming mode. Very clever!

Thanks a lot!

List of 19 messages in thread
TopicAuthorDate
Removing P89v51 Bootloader            01/01/70 00:00      
   according to the datasheet....            01/01/70 00:00      
      Thanks Jan            01/01/70 00:00      
         Maybe, but...            01/01/70 00:00      
            Bootloader v7 and PSEN            01/01/70 00:00      
               Details            01/01/70 00:00      
                  no pins needed ...            01/01/70 00:00      
                     Best solution: IAP?            01/01/70 00:00      
                        backdoor            01/01/70 00:00      
                           TxD pulled down for ISP. Clever!            01/01/70 00:00      
                        IAP            01/01/70 00:00      
                           if this is a problem            01/01/70 00:00      
                              the enhanced bootloader...            01/01/70 00:00      
                                 what enhanced bootloader            01/01/70 00:00      
                                    options            01/01/70 00:00      
                                       no, did not            01/01/70 00:00      
                                          OT: SiLabs -> NXP?            01/01/70 00:00      
                                             no, NXP ->SILabs            01/01/70 00:00      
                                          SST89V516RD/SST89E516RD for 5V/3V part            01/01/70 00:00      

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