IBM 7090 Instruction-Reference page 28

High Order
Low Order
Preset
Count
=7
Count
=6·
1st Pulse
Count
=S
2nd Pulse
Count
=4
3rd Pulse
Reset
-";"~----I~Counter
Set
Position
Step
I----il-""~ To Next Higher Position
FIGURE 3.1-4. COUNT DOWN COUNTER
FIGURE 3.1-S. BINARY COUNTER INPUTS
Adv
PC
o
o
10
7
,.
~GGGG
1
I
0 0 0
I
0
1 0
7
GGGDG
{ After Step
o
0
1
0
0 0 1
o
~
FIGURE 3.1-6. NORMAL COUNTER RIPPLE DELAY
PC
6,7,
and
a
= 1
PC9
10 &
11
Equals
1
PC12,
13 &
14
Equals
1
PC1S,
16, &
17
Equals
A
r
A
A
A
Step
PCS
Step
pca
Step
PCll
Step
PC14
Step
PC17
FIGURE 3.l-7A. PROGRAM COUNTER STEP
GENERATOR
SC12, A
Step
&13 SCll
To PCS
Off
Previou
To SCll
SC14 &
A
Step
IS Off
SC13
Previou
To SC13
To
pca
to Step
SC16 &
A
Step
17 Off
SCIS
Pre-
To SCIS
To PCll
vious to
Step Step
SC
SC17
To PC14
To SC17
FIGURE 3.1-7B. SHIFT COUNTER STEP CONTROL
To PC17
27