[Oberon] RISC5

[Jörg]

Chris

1) The RISCv5 machine has a memory of 1 MByte = 000000H.. 0FFFFFH.
   This memory is used to hold your code and store your variables.
   A dedicated region at the high end of this memory (namely from
   0E7F00H .. 0FFF00H) is called "framebuffer"; this memory region
   is used to store all pixels that are displayed on the screen.

2) The module "Display.Mod" provides all low layer routines to
   store pixels into this memory region. E.g. the procedure
   Display.Dot(col, x, y, mode: INTEGER) "draws" a dot at location
   (x/y). But it does not actually draw the point but "just" stores
   a bit in this dedicated "framebuffer" memory.

3) In parallel, the video driver "VID" (written in Verilog) permanently
   reads this special framebuffer memory and copies all bits over and
   over again to the VGA monitor. The whole framebuffer memory
   (96 kByte) is copied 70 times per second to the monitor.

Hope this helps.

br
Jörg

-----Original Message-----
From: Paul Thomas Melville [mailto:ptmelville at gmail.com] 
Sent: Donnerstag, 17. April 2014 13:46
To: ETH Oberon and related systems
Subject: Re: [Oberon] RISC5

On Thu, Apr 17, 2014 at 10:58 AM, eas lab <lab.eas at gmail.com> wrote:

> The hidden/mysterious part for me is the display/textFrames.
> Does V5 drive standard VGA?
> Where's the code showing;
>   VGA -> FrameBuffer -> ETHOviewer.

You can find information in section 9.1, 4.5 and 17.2.4 of Project Oberon.

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