IMSAI 8030
General Assembly and
Test Instructions
The switch may be raised to the RUN position starting at
any point in the loop and the processor will continue
to run at high speed beginning at the point. The
flip-flop set by the RUN/STOP .switch simply instructs
the processor to wait at each cycle for a pulse which is
generated by the SINGLE STEP switch to be received
before executing the next cycle, and apart from waiting
for this- pulse, the processor executes exactly the
same whether it is in the single run mode or stop mode.
The definition of a computer involves both the ability
to execute in sequence of instructions which is stored
inside the machine, also the ability to make a decision
between on the value of data and as a result of that
decision, choose between alternate possible paths of
program step sequences to execute. Test programs 1 and 2
involve only the execution of a sequence of stored program
steps and do not involve any decisions. Program 3 will
illustrate the use of decisions in a computer program
and should provide some interesting entertainment as well.
It is a game program using the INPUT switches and the
PROGRAMMED OUTPUT lights on the IMSAI 8080 front panel.
A pattern of lights in the PROGRAMMED OUTPUT ports is
moved to the left one bit at a time, and the left hand
bit which is "pushed off" the end of the programmed
I/O register re-appears at the right end of the register.
The rate at which the bit pattern is shifted to the left
can be chosen by the binary number set in the front
panel switches when the program is first started or when
the machine is reset to start again. When a higher
binary number is entered in these switches and program
restarted, the bit pattern will shift to the left at
a higher rate of speed. Initially, switches should be
set for 2, that is all switches down except PP.OGRAMMED
INPUT switch bit 1 on, in order that the bit pattern
will be shifted slowly enough to easily see what the
game program is doing. Once the program has been started,
the rate at which the bit pattern is shifted to the left
is not affected by any further movement of the front
panel switches. From this time on, any time any one
of the eight switches in the PROGRAMMED I/O group is
changed, then the bit in the PROGRAMMED OUTPUT port
which is directly above that switch at the momert is was
moved, will change. If it was off before, it will turn
on; and if it was on before it will turn off. The
direction of travel of the switch is not significant— only
that its position was changed. After a switch change is
detected, and the light above it turned on or off as
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