ZX Computings - OpenLibra

Hardware
DCP
M icr odevelopments
Packs
The Basic V Pack
This is 4K of dynamic RAM (2 x
6116s) to add to the basic 1K
provided with the machine.
This gives a total of 5K, the
maximum amount of memory
allowed by the system. It also
provides separate input and
output ports at the back of the
'P' pack which are memory
mapped. Because the port is
memory mapped, it can be
PEEKed and POKEd to get information
to and from the computer.
It makes no difference if
the computer is a ZX80 or a
ZX81 and it will work with a 4K
or 8K ROM. It is not possible to
connect anything else to the
computer without using a
motherboard as the only other
connectors on the 'P' pack are
0.1 molex pins for the port.
These pins are about % inch
long and there are 10 for input
and 10 for output. The pins are
connected to the eight data
lines and also provide + 5 and 0
volts. They can only drive one
TTL gate from each output pin.
The ports address is anywhere
from 21504 to 22527
as the single port replaces 1K of
RAM. The plug connections
used for the port are readily
available from other sources
than DCP.
The port can be demonstrated
by the use of switches
Stephen Adams takes a peek and
a poke inside this system which
is based on a single input/
output port and intended for a
wide range of educational and
control applications. It can be
used — with the other packs
available to plug into the port —
to monitor heatf light and
voltage, as well as activating
alarms and motors, and making
sounds.
and LEDs. A suitable circuit
diagram is included in the leaflet
that comes with the port. It is
very easy to use and comes in a
robust black plastic box 3)4 *
3% x 1% inches. Demonstration
programs are given, and
with the accompanying information
any user should find it
easy.
This is a basic building block
for DCP's control system and
although it provides only 5K of
memory, this should be more
than enough to control most
Fig. 1
RESISTOR X
KNOWN RESISTOR
devices. The port connectors
on the back are designed to be
used by two other packs 'A'
and 'C' to provide extra
facilities, but only one pack can
be used at a time.
The A' Pack
The 'A' stands for analogue and
the pack provides an interface
between the digital world of the
computer and the real world we
live in.
The 'A' pack requires a 'P'
Output from port set to 2.5 volts.
Input to 'A' pack.
0 volts.
pack or another port to work as
it cannot plug directly into tN
expansion port of the computer.
It is in a tough black bo*
like the 'P' pack, but with the input
and output sockets 2 mm
wander sockets. These wander
sockets are the same as used
on some multimeters. They
also take the connection plugs
used by schools and colleges to
connect up science experiments.
The 'A' pack is used for
measuring a voltage between 0
ZX COMPUTING SUMMER 1982
a •
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