Installation Guide

ECN 7000 Series Hardware Guide 9
convertor, whereas each expansion slot has its own convertor. Thus, the
expansion cards can be designed to use a different voltage value, as needed. See
the Edge Control Node 7000 Series Expansion Card Developer’s Guide for more
information.
The ECN main system processor can control power management for each of the
USB hubs and expansion slots. When the main processor is held in reset
(because of a watchdog or brown-out event), the expansion slots are automatically
turned off.
Software applications that run on the main processor can also control the USB
power. For example, if a particular application senses a problem with a specific
communications card, it can cycle power to that card to reset it. Alternatively,
applications can turn off individual communications cards to reduce overall
power consumption (for example, when the ECN is operating from battery back-
up power).
Watchdog and Reset
The ECN includes a number of watchdog and reset functions:
• System watchdog and reset (hardware only)
• Measurement processor watchdog (software only)
• Main system processor watchdog (software only)
• Expansion card watchdog and power control (hardware and software)
Figure 5 on page 10 shows the relationships between the various watchdog and
reset functions. The following sections describe the functions.