Echelon Series 6000 Chip databook - Manual (Page 76)

In some cases it is desirable to use the input capability of the RST~ pin to allow other
devices to reset the Series 6000 device. Examples of external devices that can be used for
this purpose include push button switches, microcontrollers, and external low-voltage
detectors.
Important: If the proper external reset circuitry is not used, the Series 6000 device can
become applicationless or unconfigured. The applicationless or unconfigured state occurs
when the checksum error verification routine detects corruption in memory which could have
been falsely detected because of an improper reset sequence.
The following guidelines must be followed in order for the Series 6000 device’s reset functions
to operate reliably:
• Any device connected to the RST~ pin must have an open-drain (or equivalent)
output. If an external device were to actively drive the RST~ pin high, contention
between that device and the Series 6000 chip’s internal circuitry could result in
anomalous behavior ranging from applicationless errors to device failure.
• If any external devices are connected to the RST~ pin of the Series 6000 chip, a
capacitor should be connected between RST~ and ground to provide noise immunity.
The value of this capacitor should be at least 100 pF, and must not exceed 1000 pF.
For even greater noise immunity, two capacitors (totaling ≤1000 pF) can be used,
with one connected from the RST~ pin to ground and the other from RST~ to V
DD33
.
These capacitors should be located within 5 mm of the Series 6000 chip’s RST~ pin.
• During board level in-circuit testing (ICT), the RST~ pin should be hard wired to
ground through a “pogo pin”.
Figure 26 shows an example reset circuit.
Series 6000 Chip
RST~
3.3 V 3.3 V
100 pF
100 pF
3.3 V
To other
devices
Figure 26. Reset Circuit
Reset Sources
Any of the following sources can cause a Series 6000 chip to reset:
• Device reset button press (or other hardware-driven assertion of the RST~ pin)
• Power-on reset
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