PIC16F631 Datasheet, PDF (143/294 Pages) Microchip Technology – 20-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F631/677/685/687/689/690
11.4.4
ENHANCED PWM
AUTO-SHUTDOWN MODE
The PWM mode supports an Auto-Shutdown mode that
will disable the PWM outputs when an external
shutdown event occurs. Auto-Shutdown mode places
the PWM output pins into a predetermined state. This
mode is used to help prevent the PWM from damaging
the application.
The auto-shutdown sources are selected using the
ECCPASx bits of the ECCPAS register. A shutdown
event may be generated by:
• A logic ‘0’ on the INT pin
• Comparator C1
• Comparator C2
• Setting the ECCPASE bit in firmware
A shutdown condition is indicated by the ECCPASE
(Auto-Shutdown Event Status) bit of the ECCPAS
register. If the bit is a ‘0’, the PWM pins are operating
normally. If the bit is a ‘1’, the PWM outputs are in the
shutdown state.
When a shutdown event occurs, two things happen:
The ECCPASE bit is set to ‘1’. The ECCPASE will
remain set until cleared in firmware or an auto-restart
occurs (see Section 11.4.5 “Auto-Restart Mode”).
The enabled PWM pins are asynchronously placed in
their shutdown states. The PWM output pins are
grouped into pairs [P1A/P1C] and [P1B/P1D]. The state
of each pin pair is determined by the PSSAC and
PSSBD bits of the ECCPAS register. Each pin pair may
be placed into one of three states:
• Drive logic ‘1’
• Drive logic ‘0’
• Tri-state (high-impedance)
REGISTER 11-2: ECCPAS: ENHANCED CAPTURE/COMPARE/PWM AUTO-SHUTDOWN
CONTROL REGISTER
U-0
ECCPASE
bit 7
U-0
ECCPAS2
R/W-0
ECCPAS1
R/W-0
ECCPAS0
R/W-0
PSSAC1
R/W-0
PSSAC0
R/W-0
PSSBD1
R/W-0
PSSBD0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
bit 6-4
bit 3-2
bit 1-0
ECCPASE: ECCP Auto-Shutdown Event Status bit
1 = A shutdown event has occurred; ECCP outputs are in shutdown state
0 = ECCP outputs are operating
ECCPAS<2:0>: ECCP Auto-shutdown Source Select bits
000 = Auto-Shutdown is disabled
001 = Comparator C1 output change
010 = Comparator C2 output change⁽¹⁾
011 = Either Comparator C1 or C2 change
100 = VIL on INT pin
101 = VIL on INT pin or Comparator C1 change
110 = VIL on INT pin or Comparator C2 change
111 = VIL on INT pin or Comparator C1 or C2 change
PSSACn: Pins P1A and P1C Shutdown State Control bits
00 = Drive pins P1A and P1C to ‘0’
01 = Drive pins P1A and P1C to ‘1’
1x = Pins P1A and P1C tri-state
PSSBDn: Pins P1B and P1D Shutdown State Control bits
00 = Drive pins P1B and P1D to ‘0’
01 = Drive pins P1B and P1D to ‘1’
1x = Pins P1B and P1D tri-state
Note 1: If C2SYNC is enabled, the shutdown will be delayed by Timer1.
© 2007 Microchip Technology Inc.
DS41262D-page 141