[A83] Re: LCD refresh rate
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[A83] Re: LCD refresh rate
If an LCD was only updated when you actually changed something, then that
would mean every pixel is continiously charged. Every pixel would need its
own circuit and switch. I don't know anything about hardware, but I think
it's technically difficult to make something like that.
And, liquid cristal has the kind habbit to keep the charge for a while and
fade out (relatively) slow. So one could charge liquid cristal pixels in
turns and still have a nice picture. Frequently refreshing the LCD is then
necessary and might indeed be steered by an interrupt.
On the 85/86, the same timer interrupt that is attached to the Z80, is used
to refresh the LCD. Some chip then copies a RAM area (FC00-FFFF) to the
screen.
On the 82/83-series an LCD-driver has its own memory map and interrupt
controller. When you write to the LCD-ports it's that memory map which gets
updated. The interrupt controller then copies that map to the LCD.
Again, these are just speculations. I don't have any proof for this.
Tijl Coosemans
----- Original Message -----
From: "Joe Pemberton" <dArkSk8eR@buffbody.com>
To: <assembly-83@lists.ticalc.org>
Sent: Friday, November 02, 2001 04:06
Subject: [A83] Re: LCD refresh rate
>
> I thought the LCD was only refreshed when you actually wrote stuff to the
> LCD ports - is the LCD driver just updated when you do that?
> Is the LCD driver really continuously refreshing the LCD? Like it has
> it's own interrupts or something?
>
References: