AMSTRAD CPC464 User Manual page 233

A custom logic array incorporates nearly all logic not already inside LSI chips; particularly timing,
colour generation and DMA circuitry.
The 6845 CRT controller device generates scanning signals for the video RAM.
NB
The mapping is intricate and changes with the screen mode. The CRTC can be used to perform
scrolling (sideways by 1140 screen width) and rolling (up and down by 8 scan lines) if the software
requires. Parameters within the CRTC select the number of lines, the frame rate, width and
positioning of the borders.
GI sound generator chip AY-3-8912: 3 voices. Sound is taken from the three channels and mixed
equally to produce a mono output on the integral loudspeaker, controlled by a volume control. There
is also an external stereo output where . . . . .
Left = Channel A + l/2 Channel C. Right = Channel B + l/2 Channel C.
This chip also receives keyboard and joystick port scan information.
An 8255 parallel I/O device interfaces the bus to the GI sound chip. It also scans the keyboard,
joystick port, option links and controls the cassette.
1.1.2)External sockets.
PCB edge connectors for general purpose expansion (12) and an external printer (12) (parallel,
Centronics). Sockets for joystick (14) (9 pin D-Type), stereo sound output (Xi), video output (10) (RGB
and sync or composite video or luminance and sync).
1.2) Outside the case.
The CPC464 system comes with a choice of two types of direct input video monitor, each includes a
5v power supply for the computer, designed to suit local mains voltage standards in the country of
sale. In addition, there is an optional PSU and UHF TV modulator, the MPl.
Cables will be required to connect to a Centronics compatible printer and Hi-fi unit.
1.3) Display specification.
The screen operates from 16K of memory. The machine has a set of 27 colours which can be freely
selected to form a palette. The number of inks on the palette depends on the screen mode. A number
of inks can be set to the same colour if required. Pixels on the screen are defined as dots of a
particular ink. (Note that the background, or paper, requires one ink from the available palette).
There is a BORDER surrounding the active picture area which can be independently set to any of
the 27 colours.
Mode Number of Inks
Normal 4
High Res 2
Multi Colour 16
NB: The computer will produce a grey scale effect if viewed on a monochrome monitor. The order of
colours in increasing brightness is as follows:-
GREY LEVEL
0 BLACK
1 BLUE
2 BRIGHT BLUE
Vert dots
200
200
200
COLOUR GREY LEVEL
Horiz dots
320
640
160
COLOUR
13 WHITE
14 PASTEL BLUE
15 ORANGE
Horiz chars
40
80
20