Datasheet

PIC18F87J90 FAMILY
DS39933D-page 272  2010 Microchip Technology Inc.
19.4.2 EUSART SYNCHRONOUS
MASTER RECEPTION
Once Synchronous mode is selected, reception is
enabled by setting either the Single Receive Enable bit,
SREN (RCSTA1<5>), or the Continuous Receive
Enable bit, CREN (RCSTA1<4>). Data is sampled on
the RX1 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 SPBRGH1:SPBRG1 registers for the
appropriate baud rate. Set or clear the BRG16 bit,
as required, to achieve the desired 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, RC1IE.
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, RC1IF, will be set when recep-
tion is complete and an interrupt will be generated
if the enable bit, RC1IE, was set.
8. Read the RCSTA1 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
RCREG1 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 19-13: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
TABLE 19-8: 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 59
PIR1 — ADIF RC1IF TX1IF SSPIF — TMR2IF TMR1IF 62
PIE1 — ADIE RC1IE TX1IE SSPIE — TMR2IE TMR1IE 62
IPR1
— ADIP RC1IP TX1IP SSPIP — TMR2IP TMR1IP 62
RCSTA1 SPEN RX9 SREN CREN
ADDEN FERR OERR RX9D 61
RCREG1 EUSART Receive Register 61
TXSTA1 CSRC
TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON1 ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 63
SPBRGH1 EUSART Baud Rate Generator Register High Byte 63
SPBRG1 EUSART Baud Rate Generator Register Low Byte 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.
CREN bit
RC7/RX1/DT1/
RC6/TX1/CK1/SEG27
Write to
SREN bit
SREN bit
RC1IF bit
(Interrupt)
Read
RCREG1
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.
RC6/TX1/CK1/SEG27
SEG28 Pin
Pin (SCKP = 0)
Pin (SCKP = 1)