15.6 PERSPECTIVE ON THE PULSE MODE APPROACH TO FSM DESIGN 795
diode D
1
is turned ON (with low resistance in forward bias) while diode D
2
is OFF (with
high resistance in reverse bias). As a result, capacitor C
1
charges up via the low resis-
tance of diode D
1
allowing node A to reach the high-voltage threshold of the RMOD
before node B. Assuming that R
2
has a greater resistance than diode D
1
in forward bias,
capacitor C
2
charges up after a time t bringing node B to the threshold voltage of the
RMOD. When both inputs to the RMOD reach the threshold (i.e., become active), the
RMOD responds by issuing an active output, X
∗
. The reverse is true for the falling edge
of the X input pulse. Now diode D
2
is ON and D
1
is OFF, resulting in a smaller time
constant at node ...