Datasheet

PIC18F47J13 FAMILY
DS39974A-page 358 Preliminary  2010 Microchip Technology Inc.
FIGURE 21-7: ASYNCHRONOUS RECEPTION
TABLE 21-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION
21.2.4 AUTO-WAKE-UP ON SYNC BREAK
CHARACTER
During Sleep mode, all clocks to the EUSART are
suspended. Because of this, the BRG is inactive and a
proper byte reception cannot be performed. The
auto-wake-up feature allows the controller to wake-up
due to activity on the RXx/DTx line while the EUSART
is operating in Asynchronous mode.
The auto-wake-up feature is enabled by setting the
WUE bit (BAUDCONx<1>). Once set, the typical
receive sequence on RXx/DTx is disabled and the
EUSART remains in an Idle state, monitoring for a
wake-up event independent of the CPU mode. A
wake-up event consists of a high-to-low transition on
the RXx/DTx line. (This coincides with the start of a
Sync Break or a Wake-up Signal character for the
LIN/J2602 protocol.)
Following a wake-up event, the module generates an
RCxIF interrupt. The interrupt is generated synchro-
nously to the Q clocks in normal operating modes
(Figure 21-8) and asynchronously if the device is in
Sleep mode (Figure 21-9). The interrupt condition is
cleared by reading the RCREGx register.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
INTCON GIE/GIEH PEIE/GIEL
TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF
PIR1 PMPIF
(1)
ADIF RC1IF TX1IF SSP1IF CCP1IF TMR2IF TMR1IF
PIE1
PMPIE
(1)
ADIE RC1IE TX1IE SSP1IE CCP1IE TMR2IE TMR1IE
IPR1 PMPIP
(1)
ADIP RC1IP TX1IP SSP1IP CCP1IP TMR2IP TMR1IP
PIR3 SSP2IF BCL2IF RC2IF TX2IF TMR4IF CTMUIF TMR3GIF RTCCIF
PIE3
SSP2IE BCL2IE RC2IE TX2IE TMR4IE CTMUIE TMR3GIE RTCCIE
IPR3 SSP2IP BCL2IP RC2IP TX2IP TMR4IP CTMUIP TMR3GIP RTCCIP
RCSTAx SPEN RX9 SREN CREN ADDEN FERR OERR RX9D
RCREGx EUSARTx Receive Register
TXSTAx
CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D
BAUDCONx ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN
SPBRGHx EUSARTx Baud Rate Generator High Byte
SPBRGx EUSARTx Baud Rate Generator Low Byte
Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.
Note 1: These bits are only available on 44-pin devices.
Start
bit
bit 7/8
bit 1bit 0 bit 7/8
bit 0
Stop
bit
Start
bit
Start
bit
bit 7/8
Stop
bit
RXx (pin)
Rcv Buffer Reg
Rcv Shift Reg
Read Rcv
Buffer Reg
RCREGx
RCxIF
(Interrupt Flag)
OERR bit
CREN
Word 1
RCREGx
Word 2
RCREGx
Stop
bit
Note: This timing diagram shows three words appearing on the RXx input. The RCREGx (Receive Buffer) is read after
the third word causing the OERR (Overrun) bit to be set.