[Oberon] System-V - Frame Clipping

Skulski, Wojciech skulski at pas.rochester.edu
Mon Mar 4 06:32:13 CET 2019


  the textbooks by Pong P. Chu discuss the video controller implementation which is doing image blending in hardware (firmware, actually). The idea is close to what you are suggesting, I think. Both these books, one in VHDL and the other in Verilog, are very well written and worth reading. I believe that good inspiration on clipping in hardware can come from reading these chapters.

Go to RiskFive.com and select the "Web Resources" section. The first two "Books and Articles" are the ones I am referring to.

From: Oberon [oberon-bounces at lists.inf.ethz.ch] on behalf of Tomas Kral [thomas.kral at email.cz]
Sent: Sunday, March 3, 2019 1:26 PM
To: oberon at lists.inf.ethz.ch
Subject: Re: [Oberon] System-V - Frame Clipping

> VAR F: Display.Frame
> Clip(F) (*clipping ON*)
> Clip(NIL) (*clipping OFF*)

RISC-5 has some reserved address space from $FFFF00 to $FFFFFF, some
used by H/W mapped registers for I/O.

I was thinking, to use some of those for `VID.v' clipping.

Procedure `Clip()' would fiddle with some of these reserved addresses.

Is it worthwhile, or
just bad idea, difficult, complex or costing many cycles, and
stalling CPU?

Tomas Kral <thomas.kral at email.cz>

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