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More VT100 groundwork

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This commit is contained in:
Jeff Parsons 2016-07-27 12:03:12 -07:00 • committed by Jeff Parsons
commit c8f5357689
11 changed files with 162 additions and 14 deletions
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3
devices/pc8080/machine/README.md
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@ -9,5 +9,6 @@ PC8080 Machine Configurations
The following 8080-based machines are currently available:
* [8080 Exerciser](exerciser/)
* [Space Invaders (1978)](invaders/)
* [8080 Exerciser Test Machine](exerciser/)
* [DEC VT100 Terminal](vt100/)

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devices/pc8080/machine/vt100/README.md Normal file
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@ -0,0 +1,59 @@
---
layout: page
title: VT100 Terminal
permalink: /devices/pc8080/machine/vt100/
machines:
- type: pc8080
id: vt100
debugger: true
---
VT100 Terminal
--------------
This is where we'll be testing another 8080-based machine: a VT100 Terminal. Unlike other VT100 emulations,
this will simulate a VT100 by running the terminal's original firmware inside the [PC8080](/modules/pc8080/) CPU emulator.
As described in the [Technical Manual (July 1982)](http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/terminal/vt100/EK-VT100-TM-003_VT100_Technical_Manual_Jul82.pdf),
p. 4-15, 8Kb (0x2000) of ROM is located at 0x0000, and 3Kb (0x0C00) of RAM immediately follows it at 0x2000.
[vt100romhax](http://vt100romhax.tumblr.com/post/90697428973/the-vt100-memory-map-and-8080-disassembly)
(aka [phooky](https://github.com/phooky)) further explains VT100 memory usage:
Start End Size Description
0x0000 0x1fff 8K Basic ROM
0x2000 0x2012 18B Blank lines for refresh (6 x 3B)
0x2012 0x204f 61B Stack area (grows down from 0x204e)
0x204f 0x22d0 641B Scratch Pad/Setup Area(?)
0x22d0 0x2c00 2352B Screen RAM
Normally, the PC8080 Video component allocates its own video buffer, based on the specified buffer address
(*bufferAddr*) and other dimensions (eg, *bufferCols* and *bufferRows*), but the VT100 is a little unusual:
it has a custom video processor that uses DMA to request character data from any region of RAM, one line at a time.
It always defaults to address 0x2000 for the first line of character data, but each line terminates with 3 bytes
containing line attributes and the address of the next line, so the location of subsequent lines will vary,
depending on the following line attributes:
* Single-width characters (80 or 132 columns)
* Double-width characters (40 or 66 columns)
In addition to single vs. double width, line attributes can also specify double height (along with whether the
top half or bottom half of the character should be displayed).
The VT100 screen displays 800 dots per horizontal scan, and a total of 240 horizontal scans,
so for optimum scaling, we define our own screen using multiples of those dimensions (currently 1600x480),
and by default, it uses a 10x10 character cell, so the default display dimensions are 80 columns by 24 rows.
In light of the above, the [machine XML file](machine.xml) must set the Video component's *bufferRAM* property
to "true", indicating that existing RAM should be used, and a new property, *bufferFormat* must be set to "vt100",
enabling support for the VT100's line data format; eg:
<ram id="ram" addr="0x2000" size="0x0C00"/>
<video id="video" screenWidth="1600" screenHeight="480" bufferAddr="0x2000" bufferRAM="true" bufferFormat="vt100" bufferCols="80" bufferRows="24" ...>
{% include machine.html id="vt100" %}
VT100 Resources
---------------
[VT100 Publications](/pubs/dec/vt100/)

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devices/pc8080/machine/vt100/machine.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="/versions/pc8080/1.23.2/machine.xsl"?>
<machine id="vt100" class="pc8080" border="1" pos="center" background="#FAEBD7">
<name pos="center">VT100 Terminal</name>
<computer id="computer" busWidth="16"/>
<cpu id="cpu8080" model="8080" cycles="2000000" autoStart="true"/>
<rom id="rom" addr="0x0000" size="0x2000" file="/devices/pc8080/rom/vt100/VT100.json"/>
<ram id="ram" addr="0x2000" size="0x02D0"/>
<video id="video" screenWidth="1600" screenHeight="480" smoothing="false" bufferAddr="0x22D0" bufferRAM="true" bufferFormat="vt100" width="40%" pos="left" padding="8px">
<menu>
<title>VT100 Screen</title>
<control type="container" pos="right">
<control type="button" binding="fullScreen" padleft="8px;line-height:1em">Full Screen</control>
</control>
</menu>
</video>
<keyboard id="keyboard"/>
<panel ref="/devices/pc8080/panel/left.xml"/>
<debugger id="debugger" commands="s 8086"/>
</machine>

2
devices/pc8080/rom/README.md
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@ -17,5 +17,5 @@ for each ROM in the machine; eg:
The project currently contains the following 8080-based ROMs:
* [8080 Exerciser Tests](exerciser/)
* [DEC VT100](vt100/)
* [Space Invaders (1978)](invaders/)
* [DEC VT100 Terminal](vt100/)

2
devices/pc8080/rom/vt100/README.md
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@ -31,7 +31,7 @@ The above PCB chip locations correspond to the following [DEC ROM](/devices/roms
* E45: [23-033E2.bin](https://web.archive.org/web/20140723115846/http://www.dunnington.u-net.com/public/DECROMs/23-033E2.bin)
* E40: [23-034E2.bin](https://web.archive.org/web/20140723115846/http://www.dunnington.u-net.com/public/DECROMs/23-034E2.bin)
And sure enough, concatenating those DEC ROM four dumps produces a perfect match for Trammell Hudson's
And sure enough, concatenating those four DEC ROM dumps produces a perfect match for Trammell Hudson's
[VT100.bin](http://trmm.net/images/2/20/VT100.bin).
The VT100 also used one 2Kb character generator ROM, which is stored in [23-018E2.json](23-018E2.json).