
Front Panel Operation
2-100
DIGITAL I/O
Overview
The Model 2002’s Digital I/O port is a 9-pin “D” sub-
miniature connector located on the rear panel. The port’s
location and pin designations are shown in Figure 2-36.
The Model 2002’s Digital I/O port can be used to control
external circuitry. The port provides four output lines and
one input line. Each open-collector output can be set high
(+5V) or low (0V) and will sink up to 100mA. A TTL high
on the Model 2002’s digital input is read as “ON”. The four
output lines can also operate external supplies from +5V to
+30V.
Use the DIGITAL I/O Menu to select the following options:
• OUTPUT-STATE
ON or OFF selectable for each output line (1 through
4). Use to check or change the output state.
• OUTPUT-SENSE
ACTIVE-HIGH or ACTIVE-LOW selectable for each
output line (TTL1 through TTL4). Use to check or
change the output sense.
• INPUT
ON or OFF. Use to check or change the status of the
digital input line. Sense is fixed at active-high
(ON=5V).
Controlling digital circuitry
Each of the four digital, open-collector outputs (connector
J1031, pins 6 through 9) includes a built-in pull up resistor to
+5V. The output transistor is capable of sinking up to 100mA
from voltages up to +30V. The outputs can be controlled
independently or tied to one of four limit values (two high,
two low). Paragraph 2.12.5 contains information about con-
trolling digital outputs from the limits menu.
Early versions of the Model 2002 have an additional 10k
Ω
resistor connected between the collector and the internal
built-in test circuitry. Under certain combinations of output
states, this resistor limits the output high to 2.5V.
For example:
Output #1 set high (+5V)
Outputs #2, #3, and #4 set low (0V)
Output #1 is restricted to +2.5V
If using the digital output to sink current from external
devices, a Model 2002 containing the additional 10k
Ω
resis-
tor will function correctly. The transistor switch is open
restricting current flow through the external device in the
high state (+5V). However, if the output is directly used as an
input to a typical logic input, the 2.5V high state may not be
reliably detected as a high. To correct this condition (if a
2.5V high is unacceptable), add external 1k
Ω
pull up resis-
tors to the logic circuit inputs, remove the built-in test resis-
tors (R734, R737, R739, and R741), or use an external
voltage supply.
External voltage supply
Each output can be operated from external voltage supplies
(voltage range from +5V to +30V applied through the device
being driven). Refer to Figure 2-37 for a simplified schemat-
ic of the digital I/O port. The high current sink capacity of the
output driver allows direct control of relays, solenoids, and
lamps, with no additional circuitry needed. Each output
channel contains a fly-back diode for protection when
switching inductive loads (such as a low power solenoid or
relay coils). To use these fly-back diodes, connect the exter-
nal supply voltage to pin 4 of J1031 (the digital I/O port).
Make sure the external supply voltage is b5V and
+30V and the current required by the device does not exceed
100mA.
Figure 2-36
Digital I/O port
1 = Digital Input
2 = N/C
3 = N/C
4 = Vext fly-back connection (+5V to 30V)
5 = Digital Ground
6 = Digital Output #1
7 = Digital Output #2
8 = Digital Output #4
9 = Digital Output #3
Digital I/O Receptacle
5
1
9
6
(Connector J1031)
Pin Designations
Содержание 2002
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