How to set states of pins in an software USART

[arunb]

Hi,


Compiler: PCM
MCU : 16F877

I have setup a software USART on pins D4, D5 of PIC 16F877. The pins are connected to the Rxd and Txd pins of a 16F628.

Kindly advise what should be the state of the pins, High, low or float.

I am currently using float I find that most of the times data is not sent at all although the pin state changes to high ( both pins). Ins pite of this I can see no pulses on my scope.

But please remember communication takes place some times.

thanks
arunb

[Ttelmah]

The transmit pin should be left high when not sending. Otherwise the receiver will not reliably see the 'start bit', which is a low.

Best Wishes

[arunb]

Hello,

Thanks for the reply.

Does the software USART do this autmatically ( making Txd high after transmission) ?? or do I have to do it ???

What about Rxd ???

thanks
arunb

[Guest]

[Ttelmah]

It is all automatic.
The 'stop' bit, is a high, and the pin is left in this state when the character is finished.

Best Wishes