Datasheet

Table Of Contents
PIC18F85J90 FAMILY
DS39770C-page 268 2010 Microchip Technology Inc.
19.4.2 AUSART SYNCHRONOUS
MASTER RECEPTION
Once Synchronous mode is selected, reception is
enabled by setting either the Single Receive Enable bit,
SREN (RCSTA2<5>), or the Continuous Receive
Enable bit, CREN (RCSTA2<4>). Data is sampled on
the RX2 pin on the falling edge of the clock.
If enable bit SREN is set, only a single word is received.
If enable bit CREN is set, the reception is continuous
until CREN is cleared. If both bits are set, then CREN
takes precedence.
To set up a Synchronous Master Reception:
1. Initialize the SPBRG2 register for the appropriate
baud rate.
2. Enable the synchronous master serial port by
setting bits, SYNC, SPEN and CSRC.
3. Ensure bits, CREN and SREN, are clear.
4. If interrupts are desired, set enable bit, RC2IE.
5. If 9-bit reception is desired, set bit, RX9.
6. If a single reception is required, set bit, SREN.
For continuous reception, set bit, CREN.
7. Interrupt flag bit, RC2IF, will be set when recep-
tion is complete and an interrupt will be generated
if the enable bit, RC2IE, was set.
8. Read the RCSTA2 register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
9. Read the 8-bit received data by reading the
RCREG2 register.
10. If any error occurred, clear the error by clearing
bit, CREN.
11. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
FIGURE 19-8: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
TABLE 19-7: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER 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 57
PIR3
LCDIF RC2IF TX2IF CCP2IF CCP1IF —60
PIE3
LCDIE RC2IE TX2IE CCP2IE CCP1IE —60
IPR3
LCDIP RC2IP TX2IP CCP2IP CCP1IP —60
RCSTA2 SPEN RX9 SREN CREN
ADDEN FERR OERR RX9D 62
RCREG2 AUSART Receive Register 62
TXSTA2 CSRC
TX9 TXEN SYNC BRGH TRMT TX9D 62
SPBRG2 AUSART Baud Rate Generator Register 62
Legend: — = unimplemented, read as ‘0. Shaded cells are not used for synchronous master reception.
CREN bit
RX2/DT2 pin
TX2/CK2 pin
Write to
bit SREN
SREN bit
RC2IF bit
(Interrupt)
Read
RCREG2
Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4Q2 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
0
bit 0 bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7
0
Q1 Q2 Q3 Q4
Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0.