Missile Width (D5,D4)
This has the effect of “stretching” the missile out over 1, 2, 4, or 8 colour clock counts (a full scan line is 160 colour clocks).
MSIZEb D5 | MSIZEa D4 | APPEARANCE | CLOCKS | DESCRIPTION |
0 | 0 | 1 | Single width | |
0 | 1 | 2 | Double width | |
1 | 0 | 4 | Quadruple width | |
1 | 1 | 8 | Octuple width |
The multiple-scanline missiles shown in the RESULT column would be formed by rewriting ENAM0 and/or ENAM1 every scanline to define the scanlines where the missile is visible.
Object Copies & Width (D2, D1, D0)
Multiple copies of players as well as their width and spacing are controlled by (D0, D1, D2) in NUSIZ0/NUSIZ1. Width changes are achieved by slowing the scan rate and stretching the 9 bits of serial graphics out over 8, 16, or 32 clocks of horizontal line time. Each player position counter has three decodes in addition to the zero crossing decode. These decodes trigger 1, 2, or 3 copies of the player (at various spacings) across a horizontal line. These same control bits are used for the decodes on the missile position counter, ensuring an equal number of players and missiles.
PSIZEc D2 | PSIZEb D1 | PSIZEa D0 | APPEARANCE | DESCRIPTION |
0 | 0 | 0 | One copy | |
0 | 0 | 1 | Two copies, close | |
0 | 1 | 0 | Two copies, medium | |
0 | 1 | 1 | Three copies, close | |
1 | 0 | 0 | Two copies, wide | |
1 | 0 | 1 | Double width player | |
1 | 1 | 0 | Three copies, medium | |
1 | 1 | 1 | Quadruple width player |
The graphics shown in the RESULT column would be formed by rewriting GRP0 and/or GRP1 every scanline to form the shape of the skull. Unless changed, the TIA will show the same bit pattern on every scanline.