VISTEK V1679, Руководство пользователя, Страница: 8 / 31

VISTEK V1679 single-mode fibre
data transceiver
8 Issue 1
3. GENERAL PURPOSE INPUTS
3.1 Description
Depending on the actual board configuration, the V1679 supports up to 16 General Purpose Inputs.
A
V1679/IO features 8 General Purpose Inputs in addition to its 8 General Purpose Outputs, whereas a
V1679/IP comes with 16 Inputs and no Outputs.
Each of the Inputs comprises an Opto-Isolator with integrated Schmitt-Trigger Buffer, amongst other features,
such as:
•
Jumper configurable on-board input biasing (+5V or +12V)
•
Jumper configurable short to ground
•
On-board, 100 Ohm current limiting resistor for Opto-Isolator
•
Reverse polarity protection
•
Wide input current range
•
High speed (up to 1Mb/s)
Various configuration options allow straightforward interfacing of the GP Inputs to a variety of 'driving'
sources'. A driving source can be as simple as a push button, an 'Open Collector' output or a TTL/CMOS-
level buffer with a current-sinking/sourcing capability of as low as ±4mA. Extra series resistors might be
required when using a voltage source of > 7V in order to limit the forward current of the Emitter Diode inside
the Opto-Isolator. Please check with your technical department or contact Vistek for a suitable solution.
Examples of different interfacing techniques will be shown later.
3.2 Configuration
The following circuit diagram shows the input circuit of each General Purpose Input. Understanding the
diagram will help in finding the proper configuration for a specific application.
100R
390R 1K8
GPIOn-
GPIOn+
+5V +12V
1N4148
Emitter Section of Opto-Isolator:
Forward Voltage V
F
: 1.5V (max) @ I
F
= 10mA
Turn-On Threshold Current I
F(ON)
: 1.6mA (max)
Continous Forward Current I
F
: 60mA (max)
Input Bias Voltage Selection Jumper
Short to GND Jumper
Notes:
Board GND = Chassis GND
Always provide a proper return-current path for your signal!
From/To 44-way High Density D-Type Connector
Protection Diode:
Forward Voltage V
F
: 1.0V (max) @ I
F
= 10mA
On-board power supplies
Figure 2 : General Purpose Inputs (Circuit Diagram)