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Clean up the CPU/ChipSet interface, and get the PC8080 Video component ready to actually do something

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This commit is contained in:
Jeff Parsons 2016-05-01 10:13:43 -07:00
commit 8c5ab8d73b
19 changed files with 1210 additions and 993 deletions
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59
devices/pc8080/machine/invaders/README.md
View file

@ -24,5 +24,64 @@ Assorted [Space Invaders Hardware Notes](#space-invaders-hardware-notes) are col
Space Invaders Hardware Notes
---
### Memory Map
0000-1FFF r ROM code
2000-23FF rw RAM
2400-3FFF rw bitmapped screen (224x256)
### I/O Map
00 r
01 r control inputs
bit 7
bit 6 right
bit 5 left
bit 4 fire
bit 3
bit 2 1 player start
bit 1 2 player start
bit 0 coin slot
02 r control inputs
bit 7 0=display coin info
bit 6 right 2
bit 5 left 2
bit 4 fire 2
bit 3 bonus (1500,1000) / preset mode
bit 2 1=tilt
bit 0-1 initial lives (3,4,5,6) / (3,4)
02 w shift count (0-7)
03 r shifted value (low then high)
03 w sound
bit 4 bonus base
bit 3 invader hit
bit 2 base hit
bit 1 base fire
bit 0 saucer
04 w value to shift
05 w sound
bit 5 flip video
bit 4 saucer hit
bit 3 invader movement 4
bit 2 invader movement 3
bit 1 invader movement 2
bit 0 invader movement 1
06 w watchdog timer clear
Note that, unlike most emulators, PC8080 (like PCjs) has a *[Bus](/modules/pc8080/lib/bus.js)* architecture,
allowing components to "plug in" different kinds of memory or memory-mapped devices at different addresses,
and to register specific functions for specific I/O ports.
For example, Space Invaders has 8Kb of ROM at addresses 0x0000 through 0x1FFF, which means that if any 8080 code
attempts to write to those addresses, nothing should happen. Unfortunately, most emulators treat the entire address
space as one contiguous array of bytes. Which means either that the ROM is susceptible to corruption *or* that every
write operation must check the address to determine its validity, which hurts the performance of *all* writes.
In PC8080 (and PCjs), all writes are equally fast, and all ROMs are fully protected. An exception is made for the
Debugger, which allows you to use the "e" command to modify ("patch") ROM code on the fly, but that is completely
outside and independent of the 8080 code being emulated.
### Other Online References
See [Computer Archeology](http://www.computerarcheology.com/Arcade/SpaceInvaders/) for an excellent collection
of materials on the original Space Invaders, including commented ROM disassemblies.

3
devices/pc8080/machine/invaders/machine.xml
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@ -9,7 +9,8 @@
<rom id="romF" addr="0x1000" size="0x0800" file="/devices/pc8080/rom/invaders/INVADERS-F.json"/>
<rom id="romE" addr="0x1800" size="0x0800" file="/devices/pc8080/rom/invaders/INVADERS-E.json"/>
<ram id="ram" addr="0x2000" size="0x2000"/>
<video id="video" screenWidth="224" screenHeight="256" frameBuffer="0x2400" interruptRate="120" rotation="90" width="40%" pos="left" padding="8px">
<chipset id="chipset" model="SI1978"/>
<video id="video" screenWidth="224" screenHeight="256" bufferAddr="0x2400" bufferCols="256" bufferRows="224" bufferBits="1" interruptRate="120" rotation="90" width="40%" pos="left" padding="8px">
<menu>
<title>224x256 Screen (Rotated)</title>
</menu>