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PIC18F4520E/MLQTP Datasheet(PDF) 216 Page - Microchip Technology |
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PIC18F4520E/MLQTP Datasheet(HTML) 216 Page - Microchip Technology |
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216 / 390 page ![]() PIC18F2420/2520/4420/4520 DS39631A-page 214 Preliminary 2004 Microchip Technology Inc. FIGURE 18-7: ASYNCHRONOUS RECEPTION TABLE 18-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION 18.2.4 AUTO-WAKE-UP ON SYNC BREAK CHARACTER During Sleep mode, all clocks to the EUSART are suspended. Because of this, the Baud Rate Generator is inactive and a proper byte reception cannot be per- formed. The auto-wake-up feature allows the controller to wake-up due to activity on the RX/DT line while the EUSART is operating in Asynchronous mode. The auto-wake-up feature is enabled by setting the WUE bit (BAUDCON<1>). Once set, the typical receive sequence on RX/DT 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 con- sists of a high-to-low transition on the RX/DT line. (This coincides with the start of a Sync Break or a Wake-up Signal character for the LIN protocol.) Following a wake-up event, the module generates an RCIF interrupt. The interrupt is generated synchro- nously to the Q clocks in normal operating modes (Figure 18-8) and asynchronously, if the device is in Sleep mode (Figure 18-9). The interrupt condition is cleared by reading the RCREG register. The WUE bit is automatically cleared once a low-to- high transition is observed on the RX line following the wake-up event. At this point, the EUSART module is in Idle mode and returns to normal operation. This signals to the user that the Sync Break event is over. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 49 PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 52 PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 52 IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 52 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 51 RCREG EUSART Receive Register 51 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 51 BAUDCON ABDOVF RCIDL — SCKP BRG16 — WUE ABDEN 51 SPBRGH EUSART Baud Rate Generator Register, High Byte 51 SPBRG EUSART Baud Rate Generator Register, Low Byte 51 Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception. Note 1: Reserved in 28-pin devices; always maintain these bits clear. Start bit bit 7/8 bit 1 bit 0 bit 7/8 bit 0 Stop bit Start bit Start bit bit 7/8 Stop bit RX (pin) Rcv Buffer Reg Rcv Shift Reg Read Rcv Buffer Reg RCREG RCIF (Interrupt Flag) OERR bit CREN Word 1 RCREG Word 2 RCREG Stop bit Note: This timing diagram shows three words appearing on the RX input. The RCREG (receive buffer) is read after the third word causing the OERR (overrun) bit to be set. |
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