Watlow CAS200 - Manual (Page 44)

Chapter 2: Installation CAS200 User’s Guide
32 Watlow Anafaze
CPU Watchdog
The CPU watchdog monitors the microprocessor. Its sink
output is located on
TB50 terminal #6. (Do not exceed the
5Vdc, 10mAdc rating for the watchdog timer.) The output
is Low (On) when the microprocessor is operating; when it
stops operating, the output goes High (Off), which de-
energizes the SSR.
The figure below shows the recommended circuit for the
watchdog timer output
.
Figure 2.18 Wiring Watchdog Timer Output
Digital Inputs
All digital inputs are transistor-transistor logic (TTL) level
inputs referenced to control common and the internal +5V
power supply of the CAS200.
The eight digital inputs are pulled up to 5Vdc with respect
to the scanner common by internal 10kW resistors when
not pulled low by an external device. In this high state, the
input is considered off. When an input is connected to the
scanner common, the input is pulled low and considered on.
Features that use the digital inputs can be user-configured
to activate when an input is either high or low.
To insure the inputs are reliably switched, use a switching
device with the appropriate impedances in the on and off
states and do not connect the inputs to external power
sources. When off, the switching device must provide an
impedance of at least 11kW in order to ensure the voltage
will rise to greater than 3.7Vdc. When on, the switch must
provide not more than 1kW impedance in order to insure
the voltage drops below 1.3Vdc.
To install a switch as a digital input, connect one lead to the
common terminal on the TB50 (terminals 3 and 4). Connect
the other lead to the desired digital input terminal on the
TB50 (terminals 43-50).
Digital inputs are used to activate various functions. See
Chapter 4, Setup on page 41.
SSR
+ 5Vdc
CPU Watchdog
(pin 1)
(pin 6)
TB50
+
-