Product specifications

Register MSB LSB
Number 7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 M3 EV
1 4/16K BLANK IE M1 M2 0 SIZE MAG
2 0 0 0 0 NAME TABLE BASE ADDRESS
3 COLOUR TABLE BASE ADDRESS
4 0 0 0 0 0 PG BASE ADDRESS
5 0 SPRITE ATTRIBUTE TABLE BASE ADDRESS
6 0 0 0 0 0 SPG BASE ADDRESS
7 TEXT COLOUR ONE TEXT COLOUR ZERO/BACKDROP
Register 0 This contains two VDP option control bits. All other bits are reserved for
future use and must be zeroes.
Bit1 M3 Mode Bit 3 (See register 1, bits 3 and 4)
Bit 0 EV External Video Enable/Disable 1 Enables External Video Input 0
Disables
Register 1 This contains seven VDP option control bits. Bit 2 is reserved for future
use and must be zero.
Bit 7 4/16k Ram Selection.
1 selects 4108/4116 RAM operation.
0 selects 4027 RAM operation.
This bit must be set to 1 on the MTX. It uses 4116 RAM chips for VRAM.
Bit 6 BLANK enable/ disable
1 enables the active display
0 causes the active display area to blank
When this bit is set to zero, the screen will show the border colour only
Bit 5 IE = Interrupt enable/disable
1 enables VDP interrupt
0 disables VDP interrupt
This subject is covered in depth in section 3
Bit 4 M1 = Mode bit 1
Bit 3 M2 = Mode bit 2
The three mode bits M1, M2 and M3 determine the graphic mode
that the VDP is currently in. The necessary bit set up required to activate
the different modes is shown in the table below.