PIC18F258-ESLASHSOSQTP datasheet(144/402 Pages) MICROCHIP

144 / 402 page

PIC18FXX8

DS41159E-page 142

16.6

Enhanced CCP Auto-Shutdown

When the ECCP is programmed for any of the PWM

modes, the output pins associated with its function may

be configured for auto-shutdown.

Auto-shutdown allows the internal output of either of

the

two

comparator

modules,

the

external

interrupt 0, to asynchronously disable the ECCP output

pins. Thus, an external analog or digital event can

discontinue an ECCP sequence. The comparator out-

put(s) to be used is selected by setting the proper mode

bits in the ECCPAS register. To use external interrupt

INT0 as a shutdown event, INT0IE must be set. To use

either of the comparator module outputs as a shutdown

event, corresponding comparators must be enabled.

When a shutdown occurs, the selected output values

(PSSACn, PSSBDn) are written to the ECCP port pins.

The internal shutdown signal is gated with the outputs

and will immediately and asynchronously disable the

outputs. If the internal shutdown is still in effect at the

time a new cycle begins, that entire cycle is

suppressed, thus eliminating narrow, glitchy pulses.

The ECCPASE bit is set by hardware upon a compara-

tor event and can only be cleared in software. The

ECCP outputs can be re-enabled only by clearing the

ECCPASE bit.

The Auto-Shutdown mode can be manually entered by

writing a ‘1’ to the ECCPASE bit.

ECCPAS: ENHANCED CAPTURE/COMPARE/PWM AUTO-SHUTDOWN

CONTROL REGISTER

R/W-0

ECCPASE ECCPAS2 ECCPAS1 ECCPAS0

PSSAC1

PSSAC0

PSSBD1

PSSBD0

bit 7

bit 0

bit 7

ECCPASE: ECCP Auto-Shutdown Event Status bit

= ECCP outputs enabled, no shutdown event

= A shutdown event has occurred, must be reset in software to re-enable ECCP

bit 6-4

ECCPAS<2:0>: ECCP Auto-Shutdown bits

000

= No auto-shutdown enabled, comparators have no effect on ECCP

001

= Comparator 1 output will cause shutdown

010

= Comparator 2 output will cause shutdown

011

= Either Comparator 1 or 2 can cause shutdown

100

=INT0

101

= INT0 or Comparator 1 output

110

= INT0 or Comparator 2 output

111

= INT0 or Comparator 1 or Comparator 2 output

bit 3-2

PSSACn: Pins A and C Shutdown State Control bits

= Drive Pins A and C to ‘0’

= Drive Pins A and C to ‘1’

= Pins A and C tri-state

bit 1-0

PSSBDn: Pins B and D Shutdown State Control bits

= Drive Pins B and D to ‘0’

= Drive Pins B and D to ‘1’

= Pins B and D tri-state

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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