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Author Topic: [83+/84+] Minimum safe LCD delay?  (Read 3805 times)

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Offline Runer112

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[83+/84+] Minimum safe LCD delay?
« on: May 19, 2011, 02:40:43 am »
What's the minimum number of cycles at 6MHz that should exist between LCD outputs to be safe on just about any calculator? I think I recall someone in IRC suggesting 66, which is what Ion's routine uses, while routines used in Axe are closer to 70. And how exactly might things like the LCD delay port, bad LCD drivers, and ALCDFIX affect the timing that should be used in such a routine?
« Last Edit: May 19, 2011, 02:45:24 am by Runer112 »
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Offline Quigibo

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Re: [83+/84+] Minimum safe LCD delay?
« Reply #1 on: May 19, 2011, 02:58:00 am »
For my calculator with a bad LCD, if I don't include the "out" commands as part of my T-state count between LCD commands, my calc stops glitching at exactly 59 T-states but I have heard 1 report that it got an occasion glitch at this speed so 60 is more conservative.  This corresponds to 71 and 72 T-states respectively if you include the out command in your count.  I'm not sure how the delay ports affect these speeds.
« Last Edit: May 19, 2011, 02:59:28 am by Quigibo »
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Offline Runer112

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Re: [83+/84+] Minimum safe LCD delay?
« Reply #2 on: May 19, 2011, 03:13:17 am »
That's without ALCDFIX applied, right? Because unless I'm mistaken, the point of ALCDFIX is to add delay to out instructions such that the LCD driver will be able to keep up with an ~66 cycle loop on any calculator.

And are you sure those numbers are right for your calculator? Because when I inspected Axe's grayscale routines, I noticed that the 4-level grayscale routine dips down to 67 cycles between two out instructions at one point (between column setting and the first output to the column). Shouldn't that cause problems then?
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