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Strange Problem communication between MSP430f5438 and Altera MAX-II CPLD EPM1270T144C5

Yatin
Intellectual 390 points


Hi,

I am using MSP430f5x series of controller. It communicates with CPLD using 16bit bus (portB). I am getting a strange problem that few bits get toggle even in DC condition (data is not changing on bus ). I tried giving 0xa5a5 as output from cpld and receive on port B. but I received a5b5. then I tried to figure it out on CRO, It started coming correctly as 0xa5a5.

This is our custom made board. I am using IAR embedded workbench as development software for MSP430.

I have tried increase drive strength and internal pullup but no use. It is not like only bit 4 getting currupted.. I have got many of bit toggle..like

 

expected                 got

0xa5a5  --->0xa5b5

0x5a5a ---> 0x5e5a

0xaaaa --> 0xaeba

0xaaaa -->0xaaba

0x0201 --> 0x0203

the out put is different at different time...

please suggest some solution

Regards,

Yatin

 

 

 

 

 

 

  • 0
    Guru 227245 points

    There ar emany possible reasons. One of them is crosstalk between lines, or parasitic capacitance. A poorly etched PCB is another possible cause

    It is also possible that you did initialize the ports wrong, or do you enable any module output for Port 3 or 4? Your code would tell. What about pullups on the lines?

    Even professionally made PCBs are not error-proof. for small series, the costs for an electrical testing adaptor are much too high, so they are usually only optically inspected. And sometimes there are shortcuts or ruptures. You can check with a multimeter for good or bad connections (resistance check).

  • 0 in reply to Jens-Michael Gross
    Intellectual 390 points

    Thanks Jens,

     

    You are correct that was a board problem.

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