PIC18F25J50 MICROCHIP [Microchip Technology], PIC18F25J50 Datasheet - Page 339

• Manufacturer Part Number: PIC18F25J50
• Description: 28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

20.2.3.2
The timing of WUE and RCxIF events may cause some
confusion when it comes to determining the validity of
received data. As noted, setting the WUE bit places the
EUSART in an Idle mode. The wake-up event causes a
receive interrupt by setting the RCxIF bit. The WUE bit
is cleared after this when a rising edge is seen on
RXx/DTx. The interrupt condition is then cleared by
reading the RCREGx register. Ordinarily, the data in
RCREGx will be dummy data and should be discarded.
FIGURE 20-8:
FIGURE 20-9:
 2011 Microchip Technology Inc.
RXx/DTx Line
RXx/DTx Line
Note 1: The EUSART remains in Idle while the WUE bit is set.
WUE bit
WUE bit
Note 1: If the wake-up event requires long oscillator warm-up time, the auto-clear of the WUE bit can occur before the
RCxIF
OSC1
RCxIF
OSC1
2: The EUSART remains in Idle while the WUE bit is set.
(1)
(2)
Special Considerations Using the
WUE Bit
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
oscillator is ready. This sequence should not depend on the presence of Q clocks.
Bit set by user
Bit set by user
SLEEP Command Executed
AUTO-WAKE-UP BIT (WUE) TIMINGS DURING NORMAL OPERATION
AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP
Q1
Sleep Ends
PIC18F46J50 FAMILY
The fact that the WUE bit has been cleared (or is still
set) and the RCxIF flag is set should not be used as an
indicator of the integrity of the data in RCREGx. Users
should consider implementing a parallel method in
firmware to verify received data integrity.
To assure that no actual data is lost, check the RCIDL
bit to verify that a receive operation is not in process. If
a receive operation is not occurring, the WUE bit may
then be set just prior to entering the Sleep mode.
Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Cleared due to user read of RCREGx
Cleared due to user read of RCREGx
Note 1
DS39931D-page 339
Auto-Cleared
Auto-Cleared