Product specifications

Graphics 2 mode is an enhancement of Graphics 1 mode providing more complex
colour and pattern displays and 32 sprites.
The video display consists of 35 planes, numbered from 34 down to 0. Working from
the 'back' of the screen to the 'front' these are listed below.
Plane number
34 External video plane - (Not used at present)
33 Backdrop plane - (This is where the border fives)
32 Pattern plane - (This is where the screen you print appears)
31 Sprite plane 31 - (This sprite has the lowest priority and will be
hidden by any of the other 31 sprites which may
cross it)
30-1 Sprite planes 30 to 1
0 Sprite plane 0 - (This sprite has the highest; priority and will appear
to pass in front of any of the other 31 sprites it may
cross)
It is important to note that the sprite planes are not active in Text mode.
Write only registers.
2.2
The VDP has eight write-only registers and one read only status register. The write-
only registers control VDP operation and determine the way in which VRAM is
allocated. Section 2 is concerned with the operation of these write only registers and
does not cover the operation of the read-only register. For brief description of how this
works and what it does see Appendix B.
Each of the eight write-only registers can be loaded using two 8-bit data transfers from
the CPU. The first byte transferred is the data byte and the second is the control byte.
The data byte can be any value between 0 to £FF (Decimal 0 to 255). The format of
the control byte to write to each of the write-only registers (numbered 0 to 7), is shown
in the table below.
Register Bits Bits Hex Decimal
Number 7, 6 5, 4, 3, 2, 1, 0 byte byte
0 1 0 0 0 0 0 0 0 £80 128
1 1 0 0 0 0 0 0 1 £81 129
2 1 0 0 0 0 0 1 0 £82 130
3 1 0 0 0 0 0 1 1 £83 131
4 1 0 0 0 0 1 0 0 £84 132
5 1 0 0 0 0 1 0 1 £85 133
6 1 0 0 0 0 1 1 0 £86 134
7 1 0 0 0 0 1 1 1 £87 135