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SMS2916
13
2028-02 4/24/98
Preliminary
Frequently the supervisory circuit will be deployed on a PC board that provides a peripheral function to a system.
Examples might be modem or network cards in a PC or a PCMCIA card in a laptop. In instances like this the peripheral
card may have a requirement for a clean reset function to insure proper operation. The system may or may not provide
a reset pulse of sufficient duration to clear the peripheral or to protect data stored in a nonvolatile memory.
The I/O capability of the RESET pins can provide a solution. The system’s reset signal to the peripheral can be fed
into the SMS2916 and it in turn can clean up the signal and provide a known entity to the peripheral’s circuits. The
figure below shows the basic timing characteristics under the assumption the reset input is shorter in duration than
tPURST. The same reset output affect can be attained by using the active high reset input.
If you happen to be using one of the more common supervisory circuits like a 1232, you might consider reducing your
component count such as illustrated below.
RESET
Input
RESET
Output
RESET
Output
2028 ILL16.0
t PURST
+5VDC
PBRST
TOL
GND
RST
RST
ST
+5VDC
ALE
RST
8051 Family Part
SCL
SDA
I/O
I/O
Vcc
24C16
RST
RST
VCC
RST
8051 Family Part
SCL
SDA
I/O
I/O
SMS2916
From This
To This
1232
ALE
WDI
GND
GND
2028 ILL18.1
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