Fixed Jekyll rendering of pages with PC8080 machines
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Jeff Parsons
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8 changed files with 190 additions and 11 deletions
137
devices/pc8080/machine/invaders/README.md
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137
devices/pc8080/machine/invaders/README.md
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---
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layout: page
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title: Space Invaders (Prototype)
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permalink: /devices/pc8080/machine/invaders/
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machines:
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- type: pc8080
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id: invaders
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---
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Space Invaders (Prototype)
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---
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This is a work-in-progress, with [Development Notes](#development-notes) below.
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{% include machine.html id="invaders" %}
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Development Notes
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---
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From [emutalk.net](http://www.emutalk.net/threads/38177-Space-Invaders):
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Space Invaders, (C) Taito 1978, Midway 1979
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CPU: Intel 8080 @ 2MHz (CPU similar to the (newer) Zilog Z80)
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Interrupts: $cf (RST 8) at the start of vblank, $d7 (RST $10) at the end of vblank.
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Video: 256(x)*224(y) @ 60Hz, vertical monitor. Colours are simulated with a
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plastic transparent overlay and a background picture.
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Video hardware is very simple: 7168 bytes 1bpp bitmap (32 bytes per scanline).
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Sound: SN76477 and samples.
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Memory map:
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ROM
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$0000-$07ff: invaders.h
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$0800-$0fff: invaders.g
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$1000-$17ff: invaders.f
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$1800-$1fff: invaders.e
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RAM
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$2000-$23ff: work RAM
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$2400-$3fff: video RAM
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$4000-: RAM mirror
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Ports:
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Read 1
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BIT 0 coin (0 when active)
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1 P2 start button
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2 P1 start button
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3 ?
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4 P1 shoot button
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5 P1 joystick left
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6 P1 joystick right
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7 ?
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Read 2
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BIT 0,1 dipswitch number of lives (0:3,1:4,2:5,3:6)
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2 tilt 'button'
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3 dipswitch bonus life at 1:1000,0:1500
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4 P2 shoot button
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5 P2 joystick left
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6 P2 joystick right
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7 dipswitch coin info 1:off,0:on
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Read 3 shift register result
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Write 2 shift register result offset (bits 0,1,2)
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Write 3 sound related
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Write 4 fill shift register
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Write 5 sound related
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Write 6 strange 'debug' port? eg. it writes to this port when
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it writes text to the screen (0=a,1=b,2=c, etc)
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(write ports 3,5,6 can be left unemulated, read port 1=$01 and 2=$00
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will make the game run, but but only in attract mode)
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I haven't looked into sound details.
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16 bit shift register:
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f 0 bit
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xxxxxxxxyyyyyyyy
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Writing to port 4 shifts x into y, and the new value into x, eg.
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$0000,
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write $aa -> $aa00,
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write $ff -> $ffaa,
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write $12 -> $12ff, ..
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Writing to port 2 (bits 0,1,2) sets the offset for the 8 bit result, eg.
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offset 0:
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rrrrrrrr result=xxxxxxxx
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xxxxxxxxyyyyyyyy
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offset 2:
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rrrrrrrr result=xxxxxxyy
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xxxxxxxxyyyyyyyy
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offset 7:
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rrrrrrrr result=xyyyyyyy
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xxxxxxxxyyyyyyyy
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Reading from port 3 returns said result.
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Overlay dimensions (screen rotated 90 degrees anti-clockwise):
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,_______________________________.
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|WHITE ^ |
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| 32 |
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| v |
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|-------------------------------|
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|RED ^ |
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| 32 |
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| v |
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|-------------------------------|
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|WHITE |
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| < 224 > |
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| |
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| ^ |
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| 120 |
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| v |
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| |
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|-------------------------------|
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|GREEN |
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| ^ ^ |
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|56 ^ 56 |
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| v 72 v |
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|____ v ______________|
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| ^ | | ^ |
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|<16> | < 118 > |16 < 122 > |
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| v | | v |
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|WHITE| | WHITE|
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`-------------------------------'
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Way of out of proportion :P
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