Dual UART Virtual Perioheral
Dan Michaels email (remove spam text)
Russell McMahon wrote:
Russell, I just checked the ubicom site and didn't see a VP
combining I2C and RS232. The older I2C peripheral required you
to shut down all the other VPs to run it. Maybe they have fixed
it - by interleaving into the other VPs - in the past year.
Also, I was not very happy with some of their older VPs. The
multichannel PWM was a disaster. We talked about it last spring
on piclist. And once you get several VPs going, things tend to
bog down. Personally, I like to run one thing at a time rather
than multiple things on the scenix, but then go like a bat out
of h*** [religious references bleeped out on piclist].
Re the RS232 VP, you will notice that it probably will not run
faster than 19200, as the divider values [loop counters] will
have non-integer values. Also, it really looks to me like the
accuracy of sampling diminishes greatly for higher baudrates.
The VPs sample the ports when the timer interrupts occur, and
these are not locked to the actual port pin changes.
So ..... makes me wonder.
You might also check how they do RAM bank switching in the VP
you are looking at. This is the real key to how the VPs work.
For multiple VPs of the same type, they have duplicate variables,
used in exactly the same manner, but located in different banks.
- Dan Michaels
"To every thing there is a season, and a time to every purpose..."
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