no uart output

Hi, I'm using the C51 compiler and running the SIO sample projects with an AT89s52 atmel microcontroller. The code compiles fine and I've run various simple I/O and timer programs successfully. When I tried to generate my own program that integarate pieces from various projects I found that I don't get any serial data out of the TX pin when using the code from the SIO and SIO2 examples.

I then tried only using the example projects and I don't get any output from those samples either. I'm viewing the output with a scope and I don't see any changes on the I/O line. The pin is floating so there isn't any possibility of some external circuit affecting the output. The datasheet states that Port3 has internal pullups so I don't expect I need any type of interface components to simply see the serial data.

Any idea what might be inhibiting the output? I'm new with the 8051 controllers so I expect its a simply problem.

I'm using a 12Mhz crystal with my hardware. Any suggestions would be appreciated.

-- Dan

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