VCC1 power rail provides power for the
digital input or output pins and is expected to be connected to the node processor. VCC1
is monitored for under-voltage and has two levels that are monitored, pre-warning
(UVCC1
xPR) and under-voltage (UVCC1
XXR/FX). The under-voltage
has one of four levels that can be programmed using register 8’h0E[4:3], UVCC1_SEL. Of
the supply rails providing external power, VCC1 is the only one considered an SBC fault
which causes a state change. When the under-voltage pre-warning event takes place an
interrupt is set, INT_6 register 8'h5C[6] and the nINT pin is pulled low. Once VCC1
reaches one of the programmed thresholds, SBC_CONFIG1 register 8'h0E[4:3], the device
transitions to restart mode and latch nRST low until VCC1 exceeds the under-voltage
rising threshold. nRST remains latched low, and the device stays in restart mode for
t
RSTN_act after clearing the UV threshold. For UVCC1, there is a filter
time, t
UVFLTR, that the under-voltage event must last longer than for the
device to enter restart mode, See
Figure 8-31 for UVCC1
behavior.