Datasheet

Table Of Contents
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 232 © 2009 Microchip Technology Inc.
19.4.2 EUSART SYNCHRONOUS SLAVE
RECEPTION
The operation of the Synchronous Master and Slave
modes is identical, except in the case of Sleep, or any
Idle mode and bit SREN, which is a “don’t care” in
Slave mode.
If receive is enabled by setting the CREN bit prior to
entering Sleep or any Idle mode, then a word may be
received while in this low-power mode. Once the word
is received, the RSR register will transfer the data to the
RCREG register; if the RCIE enable bit is set, the
interrupt generated will wake the chip from the low-
power mode. If the global interrupt is enabled, the
program will branch to the interrupt vector.
To set up a Synchronous Slave Reception:
1. Enable the synchronous master serial port by
setting bits, SYNC and SPEN, and clearing bit,
CSRC.
2. If interrupts are desired, set enable bit RCIE.
3. If the signal from the CK pin is to be inverted, set
the TXCKP bit.
4. If 9-bit reception is desired, set bit, RX9.
5. To enable reception, set enable bit, CREN.
6. Flag bit, RCIF, will be set when reception is
complete. An interrupt will be generated if
enable bit, RCIE, was set.
7. Read the RCSTA register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
8. Read the 8-bit received data by reading the
RCREG register.
9. If any error occurred, clear the error by clearing
bit, CREN.
10. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
TABLE 19-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION
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 55
PIR1
PSPIF
(1)
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE
(1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP
(1)
ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN
ADDEN FERR OERR RX9D 57
RCREG EUSART Receive Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON
ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave reception.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.