PIC16F753 Datasheet, PDF (97/238 Pages) Microchip Technology – 14/16-Pin, Flash-Based 8-Bit CMOS Microcontrollers

11.8 Auto-shutdown Control
Auto-shutdown is a method to immediately override
the COG output levels with specific overrides that
allow for safe shutdown of the circuit.
The shutdown state can be either cleared
automatically or held until cleared by software. In
either case, the shutdown overrides remain in effect
until the first rising event after the shutdown is cleared.
11.8.1 SHUTDOWN
The shutdown state can be entered by either of the
following two mechanisms:
• Software generated
• External Input
11.8.1.1 Software Generated Shutdown
Setting the GxASDE bit of the COGxASD0 register
(Register 11-7) will force the COG into the shutdown
state.
When auto-restart is disabled, the shutdown state will
persist until the first rising event after the GxASDE bit
is cleared by software.
When auto-restart is enabled, the GxASDE bit will
clear automatically and resume operation on the first
rising event after the shutdown input clears. See
Figure 11-8 and Section 11.8.3.2 “Auto-Restart”.
11.8.1.2 External Shutdown Source
External shutdown inputs provide the fastest way to
safely suspend COG operation in the event of a Fault
condition. When any of the selected shutdown inputs
goes true, the output drive latches are reset and the
COG outputs immediately go to the selected override
levels without software delay.
Any combination of the input sources can be selected
to cause a shutdown condition. Shutdown input
sources include:
• HLTimer1 output
• HLTimer2 output
• C2OUT (low true)
• C1OUT (low true)
• COG1FLT pin (low true)
Shutdown inputs are selected independently with bits
of the COGxASD1 register (Register 11-8).
Note:
Shutdown inputs are level-sensitive, not
edge-sensitive. The shutdown state
cannot be cleared as long as the
shutdown input level persists, except by
disabling auto-shutdown.
PIC16F753/HV753
11.8.2 PIN OVERRIDE LEVELS
The levels driven to the output pins, while the
shutdown is active, are controlled by the
GxASD0L<1:0> and GxASD1L<1:0> bits of the
COGxASD0 register (Register 11-7). GxASD0L<1:0>
controls the GxOUT0 override level and
GxASD1L<1:0> controls the GxOUT1 override level.
There are four override options for each output:
• Forced low
• Forced high
• Tri-state
• PWM inactive state (same state as that caused by
a falling event)
Note: The polarity control does not apply to the
forced low and high override levels.
11.8.3 AUTO-SHUTDOWN RESTART
After an auto-shutdown event has occurred, there are
two ways to have the module resume operation:
• Software controlled
• Auto-restart
The restart method is selected with the GxARSEN bit
of the COGxASD0 register. Waveforms of a software
controlled automatic restart are shown in Figure 11-8.
11.8.3.1 Software Controlled Restart
When the GxARSEN bit of the COGxASD0 register is
cleared, software must clear the GxASDE bit to restart
COG operation after an auto-shutdown event.
The COG will resume operation on the first rising
event after the GxASDE bit is cleared. Clearing the
shutdown state requires all selected shutdown inputs
to be false, otherwise, the GxASDE bit will remain set.
11.8.3.2 Auto-Restart
When the GxARSEN bit of the COGxASD0 register is
set, the COG will restart from the auto-shutdown state
automatically.
The GxASDE bit will clear automatically and the COG
will resume operation on the first rising event after all
selected shutdown inputs go false.
 2013 Microchip Technology Inc.
Preliminary
DS40001709A-page 97