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1-28
The registers are numbered 0, 1, 2 and 3 while the flip-flops within the reg-
isters are numbered in the reverse order.
The reverse order of the flip-flops
is necessary since, by convention, the most significant bit of a counter is
considered to be on the left.
1.6.4
The COUNTER Controls and Indicators
A fully expanded 580 Computer logic package contains four counters which may
be used for counting or timing functions.
Manual control of the counter is
provided by pushbuttons S (set) and R (reset).
Pushbutton S contains an in-
dicator lamp; it lights whenever the counter output is high.
Depressing pushbutton S sets the output flip-flop and loads the counter.
When
the count reaches 00, the output flip-flop is reset, and the counter
out~ut
goes
low.
The output stays low until the output flip-flop is again set (the counter
is loaded).
Automatic loading of the counter is accomplished by patching the
output through an AND gate (for time delay) to the S patch terminal.
The second
input for the patched AND gates serves as a controlling input; that is the AND
gates can be patched to make the counter operation dependent on two or more
separate output functions.
The preset load value is simply a matter of selecting the proper count while
the left thumbwheel. represents the tens count.
In the event the count is less
than 10 (0 through 9) the left thumbwheel is set to zero.
The counter is reset by patching a high to the R (reset) patch ·terminal or de-
pressing the manual reset (R) pushbutton on the computer keyboard.
1.6.5
The General Purpose PUSHBUTTONS
The six general purpose PUSHBUTTONS provided in the 580 Computer logic package
are latching-type switches whose outputs are terminated on the patch panel.
Two pushbutton controls are provided·for each switch.
The numbered pushbutton
is used to set the switch (output is high), and the adjacent pushbutton (blank)
is used to reset the switch (output low).
The numbered pushbutton also contains
an indicator which, when lit, indicates that the associated output is high.
When the output of a PUSHBUTTON is zero, depressing the blank pushbutton asso-
ciated with that output, generates a synchronized pulse (one clock period in
length) available at the output terminal.
1.6.6
The TIMER Controls
The rep-op TIMER controls (A and A) are used to manually force the timer into
the corresponding
mod~s
(A
=
IC,
A =
OP).
The A pushbutton contains an indicator
circuit which lights when the timer is in the IC mode.
1.7
READOUT DEVICES
The problem solution obtained with the 580 may be permanently recorded or
temporarily displayed on several types of readout devices.
The DVM or VOLT-
METER, discussed previously, may be used to measure steady-state computational
voltages.
In repetitive operation, the computer solution is displayed on an
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