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Added VT100 ROM disassembly

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This commit is contained in:
Jeff Parsons 2016-08-03 15:11:59 -07:00 • committed by Jeff Parsons
commit c206669589
5 changed files with 4977 additions and 2 deletions
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4
devices/pc8080/machine/vt100/README.md
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@ -24,6 +24,8 @@ p. 4-15, 8Kb (0x2000) of ROM is located at 0x0000, and 3Kb (0x0C00) of RAM immed
0x0000 contains all the VT100's 8080 code. The VT100 also contains a 2Kb character generator ROM, but that ROM is not
addressable by the CPU; it is used directly by the Video Processor.
See [DEC VT100 ROMs](/devices/pc8080/rom/vt100/) for more information about the ROMs.
[vt100romhax](http://vt100romhax.tumblr.com/post/90697428973/the-vt100-memory-map-and-8080-disassembly)
(aka [phooky](https://github.com/phooky) aka Adam Mayer) further explains VT100 memory usage:
@ -125,3 +127,5 @@ Additional VT100 Resources
--------------------------
[VT100 Publications](/pubs/dec/vt100/)
[D52 Microcontroller Disassemblers](http://www.brouhaha.com/~eric/software/d52/) ([Manual](http://www.bipom.com/documents/dis51/d52manual.html))

12
devices/pc8080/rom/vt100/README.md
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@ -35,3 +35,15 @@ And sure enough, concatenating those four DEC ROM dumps produces a perfect match
[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).
Disassembling the 8080 Code
---------------------------
Following in the footsteps of [vt100romhax](http://vt100romhax.tumblr.com/post/90697428973/the-vt100-memory-map-and-8080-disassembly),
I disassembled the ROM, using `dz80` from [D52 source code](http://www.brouhaha.com/~eric/software/d52/) ([manual](http://www.bipom.com/documents/dis51/d52manual.html)):
dz80 -80 archive/VT100.bin
This produced VT100.d80, which I renamed to [VT100.asm](VT100.asm). I also appeared to run into the same problem that
**vt100romhax** did: references to `X2000` that needed to be changed to `2000h`.

4956
devices/pc8080/rom/vt100/VT100.asm Normal file
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5
modules/pc8080/lib/chipset.js
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@ -172,6 +172,9 @@ ChipSet.SI1978 = {
* Hence the CPU component in the VT100's machine.xml is defined as:
*
* <cpu id="cpu8080" model="8080" cycles="2764798"/>
*
* Beyond that, we don't really care about that particular 8224. I only mention it because knowing the CPU frequency
* is helpful for simulating some of the other circuits below that we DO care about.
*/
ChipSet.VT100 = {
MODEL: 100.0,
@ -223,7 +226,7 @@ ChipSet.VT100 = {
* If we assume that the CPU cycle count increments once every 361.69ns, it will increment roughly 88 times every
* time LBA7 toggles. So we can divide the CPU cycle count by 88 and set LBA to the low bit of that truncated
* result. An even faster (but less accurate) solution would be to mask bit 6 of the CPU cycle count, which will
* doesn't change until the count has been incremented 64 times. See getVT100LBA() to see the chosen implementation.
* doesn't change until the count has been incremented 64 times. See getVT100LBA() for the chosen implementation.
*/
DC011: { // generates Line Buffer Addresses (LBAs) for the Video Processor
PORT: 0xC2, // write-only

2
modules/pc8080/lib/video.js
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@ -280,7 +280,7 @@ Video.VT100 = {
LINETERM: 0x7F,
LINEATTR: {
ADDRMASK: 0x0F,
ADDRBIAS: 0x10, // 1 == ADDRBIAS_LO, 0 = ADDRBIAS_HI
ADDRBIAS: 0x10, // 0x10 == ADDRBIAS_LO, 0x00 = ADDRBIAS_HI
FONTMASK: 0x60,
SCROLL: 0x80
},