First, thanks to all who responded to my original question.  I've learned a lot from the discussion, and I was able to verify what Bob Ammerman and others pointed out - even though I couldn't see it on my scope at first, the program does in fact "walk" from page 1 to page 2.

I was able to see this by writing code which exacty fills page 1 and produces one cycle of a square wave, followed by code which exacty fills page 2 and produces two cycles of a square wave (at twice the frequency), followed by a goto back to page 1.  The scope clearly shows the alternation between page 1 and 2.

So, I will switch to the PWM approach originally suggested by Bob Ammerman.  I am glad I spent some time with this anyway - I now have a clearer understanding of how the PC operates.

Also, Jinx wrote

> Ron, what range of frequencies are you putting out ? Some time
> ago I looked at using a PIC as the clock source for a sampler
> and decided that a better option was to use a 74xx4046 with
> an 8-bit controllable divider. This was able to output up to 6MHz

I'm putting out frequencies from 2 MHz down to 1 Hz - sort of a square-wave only signal generator.  However, I also want to vary the duty cycle (at least for frequencies below 1 MHz).  In addition, the user interface includes an LCD display for output and a few buttons for input, so I plan to do it all with just the PIC.

Thanks again for everyone's help - this group is a GREAT resource! 

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