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???
05/15/08 20:04
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#154802 - RS


<PRE>

I have a question related to UART1 communication through RS-485. Please look at the picture above. The micro-controller used is C8051F044R on all master and slave devices.

The slave devices are pre-programmed with unique ids 76h and 49h to start with. This unique id is stored in the flash memory of the micro-controllers and is pre-programmed before they are hooked up together.
The slave device 1 and slave device 2 have OE pin as low on power up, which means that they are set into receive mode.
The master device sets OE pin to high, which means that it is switched to transmit mode.
The master sends a string like AAh 01h CCh, which means that all slave devices, should send their unique id’s back. The slave devices respond to the master’s request. The OE pin goes low on the slave devices.
The slave device 2 should send an acknowledgement back to the master that it has the unique id as ‘49’.
The reply from slave 2 is going to be AAh 49h CCh.
The slave 1 will also get the same request from master and will try to respond to the master’s request at the same time as slave 2. The slave 1 will also try to send AAh 76h CCh.

Will the master get data like ---> AA 49h AAh CCh 76h CCh?

Will the master get reply like ---> AAh 49h CCh and then AAh 76h CCh?

Will the master get reply from slave devices like ---> AAh 76h CCh or AAh 49h CCh?

List of 18 messages in thread
TopicAuthorDate
RS            01/01/70 00:00      
   Sorry about the subject-- I should ahve typed            01/01/70 00:00      
   how do you expect that to work?            01/01/70 00:00      
      Send slave ID again..            01/01/70 00:00      
      one transmitter            01/01/70 00:00      
         maybe            01/01/70 00:00      
   Keep in mind that RS485 also...            01/01/70 00:00      
      I'd get rid of the "OE"            01/01/70 00:00      
         I agree            01/01/70 00:00      
         more to add            01/01/70 00:00      
            get rid of the OE            01/01/70 00:00      
            how can slave turn OE line high?            01/01/70 00:00      
   1 Suggesion to get slave ID            01/01/70 00:00      
      again: OE will not work            01/01/70 00:00      
         OE line connected , but not used            01/01/70 00:00      
            changes            01/01/70 00:00      
      Use ID as timer value            01/01/70 00:00      
         Use ID as timer value wil not work ...            01/01/70 00:00      

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