RA4-PIC16F628

[WernerKern]

Hi All,
i`ve made a ittle program with RA4 and RA2 with PIC16F628.( RA4 open drain...I know). I programmed with output_low(Pin_a4) and output_high(pin_a4). When I set a Output_low(pin_a2) between these two output-a4-orders, pin a4 turns low without setting any order with A4. Does the wtiting to the tris register causes this problem??
When I turn pin A4 high with programming it as an Input dummy=input(pin_A4) all is ok.
Sorry for my broken english...

Thank you in advance
Werner
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This message was ported from CCS's old forum
Original Post ID: 8176

[R.J.Hamlett]

:=Hi All,
:=i`ve made a ittle program with RA4 and RA2 with PIC16F628.( RA4 open drain...I know). I programmed with output_low(Pin_a4) and output_high(pin_a4). When I set a Output_low(pin_a2) between these two output-a4-orders, pin a4 turns low without setting any order with A4. Does the wtiting to the tris register causes this problem??
:=When I turn pin A4 high with programming it as an Input dummy=input(pin_A4) all is ok.
:=Sorry for my broken english...
:=
:=Thank you in advance
:=Werner
What is pulling RA4 up?.
Any 'bit set' operation, involves a 'read, modify, write' cycle. If RA4, is not adequately 'pulled up' (given it is an open collector drive), when read, for the 'output_low(pin_a2)' command, the pin is seen as a low, and this 'low' status, is then output.
The same will also happen with any other pin on the port (or other ports), but for these, the pin has to be driven to the 'wrong' state.

Best Wishes
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This message was ported from CCS's old forum
Original Post ID: 8177

[WernerKern]

Hi R.J.Hamlett,

thats my fault!! I`ve pulled up RA4 with 470 Ohm at 5V, but I`ve a testboard and there is a LED from portpin RA4 to ground. Portpin RA4 sees the 0,7V of the LED and says: low !!`
If I built in the diode in series with the resistor the programm also works!
Thanks !
Werner
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This message was ported from CCS's old forum
Original Post ID: 8184

[WernerKern]

Hi R.J.Hamlett,

thats my fault!! I`ve pulled up RA4 with 470 Ohm at 5V, but I`ve a testboard and there is a LED from portpin RA4 to ground. Portpin RA4 sees the 0,7V of the LED and says: low !!`
If I built in the diode in series with the resistor the programm also works!
Thanks !
Werner
___________________________
This message was ported from CCS's old forum
Original Post ID: 8186

[R.J.Hamlett]

:=Hi R.J.Hamlett,
:=
:=thats my fault!! I`ve pulled up RA4 with 470 Ohm at 5V, but I`ve a testboard and there is a LED from portpin RA4 to ground. Portpin RA4 sees the 0,7V of the LED and says: low !!`
:=If I built in the diode in series with the resistor the programm also works!
:=Thanks !
:=Werner
Good news. :-)
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This message was ported from CCS's old forum
Original Post ID: 8193