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11/03/09 05:46
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 		 #170375 - C2 debugger interface resets when ground pin is touched
In one of our new boards with 8051F340, when C2 interface is connected to run the code, code always jumps to ?C_STARTUP point whenever the ground or 5 V supply point of the card is touched with hand. But when single stepped once, then it jumps to some point where it is it not supposed to. The instruction is an LJUMP, but it jumps to a different point! C2/CK point of debugger is directly connected to RST of the chip, and the same point is pulled up to Vcc. Without using the debugger, board works fine. Vcc of the chip is decoupled behind the chip itself with a 0.1. Supply point is decoupled at source with 3.3 tantallum and 0.1. Ferrite bead is used after the regulator (LM317 for 3.3ing from 5volt source). Source is a linear regulator with 5 volts DC output. Board has just the chip + optoed I/Os + one MAX 232 which is used to connect to a GSM modem. The 50 Hz noise from body seems to be affecting C2 debugger in debug mode.

Kindly comment..

List of 30 messages in thread
TopicAuthorDate
C2 debugger interface resets when ground pin is touched            01/01/70 00:00      
   Flash operations            01/01/70 00:00      
      one point            01/01/70 00:00      
         WDT and flash            01/01/70 00:00      
            do you have a 4 layer board, is the PC and ...            01/01/70 00:00      
               GSM modem, not PC..            01/01/70 00:00      
                  Floating signals            01/01/70 00:00      
                  PC "ground" loop?            01/01/70 00:00      
                     That is a good point!!            01/01/70 00:00      
                  Perhaps you should "AC-couple" signal GND to "earth"            01/01/70 00:00      
   Maybe your compy USB is flakey?            01/01/70 00:00      
      apples and oranges            01/01/70 00:00      
   No surprise at all!            01/01/70 00:00      
      Actually, it resets when I am nowhere near it also.            01/01/70 00:00      
         Unfortunately,...            01/01/70 00:00      
         Section 11.3 of the datasheet            01/01/70 00:00      
            known as 'design specifications'            01/01/70 00:00      
               Another clarification..            01/01/70 00:00      
               Design specs eh            01/01/70 00:00      
                  which is ridiculous and "asking for it"            01/01/70 00:00      
                     SICKLabs...            01/01/70 00:00      
                     /RST cap            01/01/70 00:00      
   Your power supply looks instable?            01/01/70 00:00      
      Unstable supply?            01/01/70 00:00      
         Supply            01/01/70 00:00      
            wrong approach            01/01/70 00:00      
         good catch AP            01/01/70 00:00      
      Indeed!            01/01/70 00:00      
      An easy test            01/01/70 00:00      
         oh, but it does            01/01/70 00:00      

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