Global Specialties PB-502 - Manual - Manual (Page 9)

9
DESCRIPTION OF OPERATING CONTROLS AND MAJOR
COMPONENTS
In order to properly use the full capabilities of the PB-502, it is highly recommended that
the user become familiar with the controls associated with this instrument.
Power Receptacle
Five (5) pin DIN type receptacle power supply connection..
Power Switch
Push power switch S10 up to apply power to the PB-502, move switch back to turn
power off. LED Dl lights to show power ON condition.
CMOS/TTL Switch
Selector S8, is made up of three individual breadboarding tie points, and determines the
operating voltage of the PB-502 circuitry. For 12 volt operation, install a jumper wire
from the center tie point to the upper tie point labeled CMOS. In this condition, the
output amplitude of the Logic Switches, Pulsers, Clock, and Vcc tie point is 12 volts, and
the input thresholds to the Seven-Segment displays and Logic Indicators are set to 12
volts CMOS levels.
For 5 volt operation, install the jumper wire from the center tie point to the lower tie
point labeled TTL. This will cause the output amplitude of the Logic Switches, Pulsers,
Clock, and Vcc tie point to be 5 volts, and the input thresholds to the Seven Segment
Displays and Logic Indicators to be set to levels usable for TTL or CMOS operating at 5
volts.
CAUTION
A jumper must be installed selecting either the CMOS or
TTL position before power is applied, and power must be
removed when it is desired to change the selection.
Logic Indicators
The eight LEDS L0-L7, are used for indicating logic states of circuit points. A logic 1 on
a logic indicator input will light its corresponding LED. In addition, the logic indications
can be latched to freeze the states shown; a high-to-low transition on Clock X will latch
LEDs LO through L3, and a high-to-low transition on Clock Y will latch LEDs L4 through
L7. While Clock X or Clock Y remain low, the logic indications will remain latched;
bringing these points high will restore the indicators to a real time display.
Seven-Segment Displays
DS1 and DS2 are two independent seven-segment numeric displays. These are
enabled, or turned on, by applying a logic 1 to the Display Enable tie-points DS1DE for
DS1, DS2DE for DS2. When enabled, the displays will show a zero if no other inputs
are present. Numbers are displayed by applying a logic 1 to the D, C, B and A tie-points
in BCD, from 0000 to 1001. Input of 1010 or greater will cause the display to blank. The