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PIC18F2420 Datasheet(PDF) 3 Page - Microchip Technology

Part No. PIC18F2420
Description  28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
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Maker  MICROCHIP [Microchip Technology]
Homepage  http://www.microchip.com
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PIC18F2420 Datasheet(HTML) 3 Page - Microchip Technology

 
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© 2005 Microchip Technology Inc.
DS80209D-page 3
PIC18F2420/2520/4420/4520
6.
Module: ECCP
When the ECCP1 auto-shutdown feature is con-
figured for automatic restart by setting the PRSEN
bit (PWM1CON<7>), the pulse terminates immedi-
ately in a shutdown event. In addition, the pulse
may restart within the period if the shutdown
condition expires. This may result in the generation
of short pulses on the PWM output(s).
Work around
Configure the auto-shutdown for software restart
by clearing the PRSEN bit (PWM1CON<7>). The
PWM
can
be
re-enabled
by
clearing
the
ECCPASE bit (ECCP1AS<7>) after the shutdown
condition expires.
Date Codes that pertain to this issue:
All engineering and production devices.
7.
Module: ECCP
When monitoring a shutdown condition using a bit
test on the ECCPASE bit (ECCP1AS<7>), or
performing a bit operation on the ECCPASE bit,
the device may produce unexpected results.
Work around
Before performing a bit test or bit operation on the
ECCPASE bit, copy the ECCP1AS register to the
working register and perform the operation there.
By avoiding these operations on the ECCPASE bit
in the ECCP1AS register, the module will operate
normally.
In Example 1, ECCPASE bit operations are
performed on the W register.
EXAMPLE 1:
Date Codes that pertain to this issue:
All engineering and production devices.
8.
Module: ECCP
The auto-shutdown source, FLT0, has inverse
polarity from the description in Section 16.4.7
“Enhanced PWM Auto-Shutdown” of the Device
Data Sheet. A logic high-voltage level on FLT0 will
generate a shutdown on ECCP1.
Work around
None.
Date Codes that pertain to this issue:
All engineering and production devices.
9.
Module: ECCP and CCP
The CCP1 and CCP2 configured for PWM mode,
with 1:1 Timer2 prescaler and duty cycle set to the
period minus 1, may result in the PWM output(s)
remaining at a logic low level.
Clearing the PR2 register to select the fastest
period may also result in the output(s) remaining at
a logic low output level.
Work around
To ensure a reliable waveform, verify that the
selected duty cycle does not equal the 10-bit
period minus 1 prior to writing these locations, or
use 1:4 or 1:16 Timer2 prescale. Also, verify the
PR2 register is not written to 00h.
All other duty cycle and period settings will function
as described in the Device Data Sheet.
The ECCP and CCP modules remain capable of
10-bit accuracy.
Date Codes that pertain to this issue:
All engineering and production devices.
10. Module: ECCP
ECCP1
configured
for
auto-shutdown
with
Comparator 1 corrupts the PWM duty cycle pulse.
In addition, it does not always synchronize the
pulse to the beginning of the period and the end of
the pulse can occur at any time within the period.
Work around
Use FLT0 for the auto-shutdown source. Applica-
tions which can tolerate a shutdown response time
of several TCYs may use the comparator interrupt
flag to detect a shutdown event and disable the
PWM
by
clearing
the
EECPASE
bit
(ECCP1AS<7>).
Date Codes that pertain to this issue:
All engineering and production devices.
11. Module: ECCP
When the shutdown state of the PWM pin(s) is
configured to tri-state the outputs, the device may
consume higher than expected current during the
shutdown event.
Work around
Configure the PWM output for either a high or low
logic
state
during
the
shutdown
via
the
PSSAC1:PSSAC0 (ECCP1AS<3:2>) and PSSBD1:
PSSBD0 (ECCP1AS<1:0>) bits. Clearing the auto-
shutdown event will return the device to normal
current consumption levels.
Date Codes that pertain to this issue:
All engineering and production devices.
MOVF
ECCP1AS, W
BTFSC
WREG, ECCPASE
BRA
SHUTDOWN_ROUTINE


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