TC32M TELCOM [TelCom Semiconductor, Inc], TC32M Datasheet - Page 4

• Manufacturer Part Number: TC32M
• Description: ECONOMONITOR - 3-PIN SYSTEM SUPERVISOR WITH POWER SUPPLY MONITOR AND WATCHDOG
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

TC32M
DETAILED DESCRIPTION
guard stable processor operation: precision processor moni-
tor, watchdog sanity timer and external override reset
control.
Processor Monitor
below the nominal threshold voltage. As a result, this pin is
LOW when power is initially applied, holding the processor
in its reset state. RS remains low for a minimum of 500msec
after V
processor to stabilize.
Watchdog Timer
(I/O) line in series with an resistor voltage divider to V
Pulling the bottom resistor of this divider low results in an
internal voltage change ( strobe ) sufficient to reset the watch-
dog timer, but above the V
RESET pin. The processor must continuously apply strobes
in this manner within a set period to verify proper software
execution. A momentary reset (500msec minimum) is gen-
erated by the TC32M if a hardware or software failure keeps
RS from being strobed within the watchdog timeout period.
This action typically initiates the processor's power-up rou-
tine. If the interruption persists, new reset pulses are gener-
ated each timeout period until RS is strobed. This timeout
period is typically 700msec.
in a section of the program that executes frequently enough
5-6
TC32M
The TC32M provides three important functions to safe-
The RS pin is immediately driven low any time V
The processor drives the RS pin with an input/output
The software routine that drives the RS strobe must be
DD
is within tolerance to allow the power supply and
RS
R1, 10k
MICROCONTROLLER EXAMPLE
RESET
R2,10k
IL
input threshold of the processor
Figure 4. TC32M Hardware Connections (R1, R2 chosen to Meet V
CONTROLLER
PO.1
RESET
MICRO-
5V
ECONOMONITOR™ – 3-PIN SYSTEM SUPERVISOR
WITH POWER SUPPLY MONITOR AND WATCHDOG
DD
DD.
is
TC32M
R1, 10k
so the time between toggles is less than one watchdog
timeout period. The strobe signal can be derived from
microprocessor address, data and/or control signals. Typi-
cal circuit examples are shown in Figure 4.
Resistor Value Selection
valid low strobe level (V
line is low. The use of 10k , 5% tolerance resistors are
recommended. These values result in a nominal strobe level
of 2.5 on RS (min/max of 2.13V / 3.08V, assuming V
5.0V 10%). Other resistor values can be used, so long as
the additive tolerances of the power supply and resistor
values result in a strobe that falls within V
all additive tolerance conditions.
External Override Reset Control
(PB) or other electronic signal to be wire-ORed to this pin as
an external RESET override control. The external
RESET is required to be an active low signal. Internally, this
input is timed to provide a minimum RESET pulse width of
500msec. Reference Figure 2.
Supply Monitor Noise Sensitivity
going changes in V
of electrical noise on V
may require a 0.01 F bypass capacitor to reduce detection
sensitivity. This capacitor should be installed as close to the
TC32M as possible to keep the capacitor lead length short.
RS
The values of R1 and R2 must be chosen to ensure a
A built-in debounce circuit allows a push-button switch
The TC32M is optimized for fast response to negative-
5V
R2, 10k
RESET
DECODER
DD
MICROPROCESSOR EXAMPLE
. Systems with an inordinate amount
TELCOM SEMICONDUCTOR, INC.
STH
DD
STL
, V
(such as systems using relays),
) on RS when the processor I/O
STL
)
STH
ADDRESS
RESET
PROCESSOR
and V
MICRO-
STL
under
DD
=