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The Technocratic Times 2
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1988-12-31
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63 lines
PARALLELL I/O
Why be so addicted to the software? The
Amiga has a lot of possibilities for
external devices, but many people have
not imagined how easy it is to use a
computer to controlling and measuring.
The needed intergrated circuits is both
cheap and easy to use. The easiest way
is to use the parallellconnector, which
can be expanded to max. 56 I/O-lines
(7*8). The circuit in this article can
adress 24 I/O-lines (3*8), but can be
modified for more lines. You can find
the pinconfiguration of the parallell-
connector in the manual you got when
you bought your Amiga, in the chapter
"Technical Reference".On the parallell-
port can you find 25 pins, the pins of
interest for this project is: The data-
bits, D0 to D7,which contains the data-
bits that is written on the parallell-
port. The BUSY, POUT and SEL, which can
be programmed to leave a three bit
adresscode. +5V PULLUP, to supply the
circuit with power, but be careful, if
you takes to much current will the fuse
in your transformer burn. You should
also be sure that a signal or pullup is
not connected to ground, which will
result in a blowed fuse or in serious
cases, a damaged computer. The SIGNAL
GROUND pins can you use to ground your
circuit, but DO NOT connect these
signals to the shieldground, that is
availiable on the chassi of your Amiga,
it will hurt your dear Amiga badly.Lets
go on with descibe the function of this
circuit. The output lines BUSY, SEL and
POUT is used to leave a three bit
address-selectioncode to the binary
decoder IC1. The octal busbuffer IC2 is
the inputport at address $2. The latch
IC4, is the outputport at adress $3.The
transciever IC3 is a two-way directed
port at the addresses $0 (write) and $1
(read).The three left addresslines (E4,
E5 & E6) can be used to get 24 (3*8=24)
more I/O-lines. Line 7 on IC1 is not
used to select an address, but to lit
the LED D1, READY, when none of of the
addresses on the I/O-expansion have
selected. Notice that the IC3 is no
latch, which means that it only sends
data as long as it to from the computer
The Outputport IC4 has a latch and will
therefor keep the databyte stabile on
the outputline until it is overwritten
by the processor.I will now explain how
to make the software to this project.