Lesson 9: Bus and Input-Output
From the original article in Radio-Electronics
by Jonathan A. Titus
The Data Input Multiplexer module controls the
now of all data into the computer.
All data going into the computer is placed on
the I/O bus during the IN cycle signalled by
the IN signal. Since data may be coming in
from a number of different experiments or
sources, we must have some means of
selecting which data is fed into the CPU .
Two basic multiplexers are used for this
precise gating of data . The two 8263 quad,
three-line to one-line multiplexers control
which of three sets of input lines are
selected . Note that two sets of these input
lines are input ports 0 and 1. These are the
two external data input ports. The third set
of data input lines comes from the memory.
Data or instructions in the memory, all go
through the multiplexer and into the CPU.
Read More: Mark-8 Construction.pdf, p.3 [2.54 MB]
The Output Latch module is used to send
data from the computer to some external
device or instrument, such as a teletype or
perhaps the Radio-Electronics TV Typewriter
(Radio-Electronics, September 1973).
Four output latches are provided on the
Output Latch module and two of these
modules may be used with the Mark-8. The
second module may, however, only use
three of the output latches.
Read More: Mark-8 Construction.pdf, p.4 [2.54 MB]
The Mark-8 bus included 40 lines, divided into power lines, 3 input and 8 output lines, memory address lines,
interrupt lines, and multiple lines carrying control signals. See the one-page summary "Mark-8 Bus Signal
Description" by L.L. Plate
Read More: Mark-8 Bus Signal Description.pdf, p.4 [32.5 KB]