Functional Description - PEP Modular Computers Modular Computers RS485 User Manual

SMART I/O User's Manual

4.1.5 Functional Description

Figure 4.1.5.1: SM-DIN1 Schematic Diagram
+Vcc (24V)
Gnd (common)
The input circuit comprises a Zener diode requiring 3mA to drive it beyond
the 'knee' that borders between 'OFF' and 'ON'. More simply, input
voltages between 8V and 10V DC produce an unknown digital result.
After the optoisolation part of the circuit, an R-C first-order, low-pass filter
prevents noise and signals greater than 200Hz from entering the system
digital input. This filter is factory set on all channels but may be altered to a
value according to customer specifications.
The LED driver activates the relevant LED when the input exceeds 10V DC.
As previously mentioned, the last channel is capable of issuing IRQx inter-
rupts when enabled by software. This interrupt will only be acknowledged
under OS-9 if the module is on the SMART-BASE or occupies the first slot
of the first attached SMART-EXT unit. This channel is factory set at 200Hz
but higher frequencies may be catered for. The table below shows the solder-
jumper settings for this filter configuration.
Jumper S e t t i n g s
J1
J2
Page 4 - 8
User/Input
Interface
Input
Circuit
1-2 Standard input filter 200Hz
1-3 Customer specific input filter
1-2 Standard input filter 200Hz
1-3 Customer specific input filter
©1996 PEP Modular Computers GmbH
Chapter 4 Digital Modules
System
Interface
Low
LED
Digital
Pass
Driver
Input
Filter
Description
System
Interface
March 12, 1996