Aha!   I new this would come up sooner or later...

I haven't played assembler for about 10 years, so I just bought a PicStart-Plus kit to work on a project in hand - which requires large format animated alphanumeric displays (about 30 panels)

Just doing the preliminary number crunching, I came out with quite respectable results for the multiplexing - 

256 columns (8 bits per column)
CPU clock @ 4MHz
100Hz refresh rate

Provides enough time for almost 40 (16Cxx) instructions per column scanned.

If the comms is handled inbetween scans, the interruption should be minimal for most applications.
Say 9600bps / message is 256bytes (close enough), then the comms should happen in about 0.3s

Although I concede that cranking the clock up to 10MHz provides a lot more room for animation etc, where bit patterns need to be processed on the fly for all columns in each scan (updating the contents of the display more than 25 times/sec is pointless, as the viewer will never see it), so there is more time available than appears - if I'm not wrong ???

I think that's what I wanted to say...

Anyway, if anyone feels like sharing some of their source code - feel free... :) 


Michael Coop
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email   mcoop@pop.jaring.my