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Z80 & 68k Assembly =>
z80 & ez80 Assembly
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travise
Newbie
Joined: 31 Aug 2009
Posts: 9
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 Posted: 09 Sep 2009 12:34:29 pm Post subject: |
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Michael wrote: That's because during a crash, the calculator is going haywire executing who-knows-what and jumping all over and writing bytes everywhere. As just another area of RAM, the LCD memory mapping area will be just as corrupted as everything else. It is somewhat harder during a crash to write coherently to port 10h.
Cool... yeah, I pretty much figured that that was the explanation. |
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FloppusMaximus
Advanced Member
Joined: 22 Aug 2008
Posts: 472
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| Posted: 09 Sep 2009 03:13:05 pm Post subject: |
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| True. However, 2.0V has the convenient (if rather strange) feature that the ISR will copy E000 to the LCD every few interrupt cycles, so long as the run indicator is enabled. So if you really do start writing garbage all over the place, there's a decent chance that it will show up on the screen eventually. |
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calc84maniac
Elite
Joined: 22 Jan 2007
Posts: 770
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| Posted: 09 Sep 2009 03:50:44 pm Post subject: |
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| Now we need to make a contraption that uses the 0 and 1 keys as a link port... :biggrin: |
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TheStorm
Calc Guru
Joined: 17 Apr 2007
Posts: 1233
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| Posted: 09 Sep 2009 07:05:04 pm Post subject: |
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| Don't the newer one's have a space on the Board to solder a Link port, or is that not hooked up to anything? |
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FloppusMaximus
Advanced Member
Joined: 22 Aug 2008
Posts: 472
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| Posted: 09 Sep 2009 08:05:54 pm Post subject: |
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Yes, there is a space for a link port (the PCB is identical to that of the original TI-82.) Apart from the jack itself, there are a few resistors and transistors missing. I haven't investigated in detail, but my guess would be that - as on the TI-82 - Z80 port 0 controls four independent GPIO lines, which you could theoretically connect to whatever you wanted. See 82-ports.txt for a schematic of how the TI-82's link port is connected.
Last edited by Guest on 09 Sep 2009 08:06:35 pm; edited 1 time in total |
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magicdanw
pcGuru()
Calc Guru
Joined: 14 Feb 2007
Posts: 1110
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| Posted: 10 Sep 2009 01:59:59 am Post subject: |
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Just wanted to let y'all know this is a pretty sick method you've got going for you. Reminds me of the early iPod hacking, where clicks and beeps from the iPod were recorded into a computer microphone and used to dump the software  |
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travise
Newbie
Joined: 31 Aug 2009
Posts: 9
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| Posted: 11 Sep 2009 09:39:44 pm Post subject: |
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Speaking of the LCD driver used in the later 81s, I wonder if this means the earlier 81s using a memory-mapped LCD were therefore immune to the odd flickering/flashing effect that my V2.0V TI-81 exhibits when I repeatedly clear the screen then print something from a program, which I assume is probably caused by the synchronization between the LCD state and the relatively infrequent updates to the driver.
For instance, the following program:
Code:
:0→X
:Lbl 0
:ClrHome
:Disp ""
:Disp X
:X+1→X
:X/100→Y
:Lbl 1
:DS<(Y,0
:Goto 1
:Goto 0
causes a different flashing effect every 100 loops, sometimes causing the screen to appear totally blank for several seconds straight. Sometimes, depending on timing and luck, *partial* characters can even be seen.
Last edited by Guest on 11 Sep 2009 09:40:34 pm; edited 1 time in total |
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FloppusMaximus
Advanced Member
Joined: 22 Aug 2008
Posts: 472
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| Posted: 12 Sep 2009 01:40:25 pm Post subject: |
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Weird. Yeah, that probably is the explanation.
I imagine that TI's programmers were trying to save space by writing the OS this way; the ROM is only 32k and doesn't have any space to spare. Which makes me wonder why they would have switched to the 82-style hardware at all, but maybe it really was significantly cheaper. |
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