A82: Coloumns 12-14 (Was: Re: Dead list, huh?)
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A82: Coloumns 12-14 (Was: Re: Dead list, huh?)
Pretty nice site, and quite a lot of programs. The information on the
display controller is mostly correct, but I thought I would try to explain
what is going on anyway.
The display controller used by the TI82 is a Toshiba T6A04, which is
intended to drive a 120x64 LCD. The display controller includes 7.5 kbits
RAM, which is directly mapped to the LCD. On the TI82 the diaply is 96x64,
which means that the last 24 coloumns is not used. Since this part of the
RAM is never shown on the display using it for data storage is possible.
There are two different ways to acces the display controller, either 8 bit
mode or 6 bit mode. The TI82 always uses 8 bit mode, which mean that each of
the 8 bits written to the controller is mapped to a pixel (8 pixels/byte).
The other mode is 6 bit mode where the first 6 bits are mapped to a pixels,
and the last two are ignored. In 8 it mode the coloumn counter goes from 0
to 14, in 6 bit mode it goes from 0 to 19. So the extra columns can be
accessed as coloumns 12-14 in 8 bit mode and 16-19 in 6 bit mode.
So what type of memory is used in the display controller ? According to the
data sheet from Toshiba the memory is RAM, so as soon as the power supply is
turned of, the memory is deleted. It is however noted in the data sheet that
sending the off command to the display controller has no effect on the
contence of the RAM, and the standby command should also leave the RAM
unchanged. Using one of the status on the Z80 it is possible to turn off the
display controller by turning of the powersupply to the IC. This should
delete the contence of the RAM. If the power supply is left on the display
controller uses ~ 5 microW. I do not remember what method APD and 2nd OFF
uses to turn off the display controller, but I assume they cut the power
supply.
Can one assume that data stored in the display controller memory will remain
there in case of an APD or 2nd OFF ? I would not think so, but I have not
checked this. When the calc APDs the contence of the display controller
memory is copied to the APD_BUF, and the display is turned off, why would
this be done if the contents of the RAM was not changed ?
If any one is interested in using the display controller directly, getting a
copy of the datas sheet might be a good idea.
Dines
----- Original Message -----
From: Jeremy Wazny <j.wazny@ugrad.unimelb.edu.au>
To: <assembly-82@lists.ticalc.org>
Sent: Sunday, February 21, 1999 7:07 AM
Subject: A82: Dead list, huh?
>
>I too have noticed that the 82ASM list has gone kinda quiet; it doesn't
>take very much of an effort.... Given that, I thought I might mention my
>new 82 web page which you can find at:
>cassius.its.unimelb.edu.au/~jeremyrw
>Basically it's all about the stuff I've done on hte 82 in assembly, my
>current "projects", and some functions and info that I've written along
>the way. Also, info about using columns 12-14 of the display controller to
>store data (bet you didn't know you could do that...). Anyway, that's at
>least one good reason to check it out, so if you've got the time please
>help me get more than the current 11 hits that the site already has.
>Thanks
>Jeremy
>
>Ummm... as for the "porn", uhhh "game"... well, I probably shouldn't say
>anything.
>
>