Pepper Computer RS485, RS232 user manual Functional Description, SM-DIN1 Schematic Diagram

SMART I/O User’s Manual Chapter 4 Digital Modules

4.1.5 Functional Description

Figure 4.1.5.1: SM-DIN1 Schematic Diagram

User/Input

Interface

+Vcc (24V)

Input

Circuit

Gnd (common)

Low

Pass

Filter

System

Interface

Digital

Input

LED

Driver

System

Interface

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.

Page	4 - 8	Jumper S e t t i n g s			Description	March 12, 1996
			J1	1-2	Standard input filter 200Hz
				1-3	Customer specific input filter
			J2	1-2	Standard input filter 200Hz
				1-3	Customer specific input filter
				©1996 PEP Modular Computers GmbH