PIC18F45J50-I/SOSQTP データシートの表示（PDF） - Microchip Technology

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PIC18F45J50-I/SOSQTP

28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology

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PIC18F46J50 FAMILY

20.2.3.2 Special Considerations Using the

WUE Bit

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.

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.

FIGURE 20-8:

AUTO-WAKE-UP BIT (WUE) TIMINGS DURING NORMAL OPERATION

OSC1

WUE bit(1)

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

Bit set by user

Auto-Cleared

RXx/DTx Line

RCxIF

Cleared due to user read of RCREGx

Note 1: The EUSART remains in Idle while the WUE bit is set.

FIGURE 20-9:

AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

OSC1

WUE bit(2)

Bit set by user

RXx/DTx Line

RCxIF

SLEEP Command Executed

Q1

Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

Auto-Cleared

Sleep Ends

Note 1

Cleared due to user read of RCREGx

Note 1:

2:

If the wake-up event requires long oscillator warm-up time, the auto-clear of the WUE bit can occur before the

oscillator is ready. This sequence should not depend on the presence of Q clocks.

The EUSART remains in Idle while the WUE bit is set.

 2011 Microchip Technology Inc.

DS39931D-page 339

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