PIC18F4550-IP Datasheet, PDF (264/438 Pages) Microchip Technology – 28/40/44-Pin, High-Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
20.3.2 EUSART SYNCHRONOUS
MASTER RECEPTION
Once Synchronous mode is selected, reception is
enabled by setting either the Single Receive Enable bit,
SREN (RCSTA<5>), or the Continuous Receive
Enable bit, CREN (RCSTA<4>). Data is sampled on the
RX 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 SPBRGH:SPBRG 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 the signal from the CK pin is to be inverted, set
the TXCKP bit. If the signal from the DT pin is to
be inverted, set the RXDTP bit.
5. If interrupts are desired, set enable bit, RCIE.
6. If 9-bit reception is desired, set bit, RX9.
7. If a single reception is required, set bit, SREN.
For continuous reception, set bit, CREN.
8. Interrupt flag bit, RCIF, will be set when reception
is complete and an interrupt will be generated if
the enable bit, RCIE, was set.
9. Read the RCSTA register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
10. Read the 8-bit received data by reading the
RCREG register.
11. If any error occurred, clear the error by clearing
bit, CREN.
12. If using interrupts, ensure that the GIE and PEIE bits
in the INTCON register (INTCON<7:6>) are set.
FIGURE 20-13: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
RC7/RX/DT/SDO
pin
bit 0
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
RC6/TX/CK pin
(TXCKP = 0)
RC6/TX/CK pin
(TXCKP = 1)
Write to
bit SREN
SREN bit
CREN bit ‘0’
‘0’
RCIF bit
(Interrupt)
Read
RXREG
Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0.
TABLE 20-8: 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
53
PIR1
SPPIF⁽¹⁾ ADIF
RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF
56
PIE1
SPPIE⁽¹⁾ ADIE
RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE
56
IPR1
SPPIP⁽¹⁾ ADIP
RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP
56
RCSTA
SPEN
RX9
SREN CREN ADDEN FERR OERR RX9D
55
RCREG EUSART Receive Register
55
TXSTA
CSRC
TX9
TXEN SYNC SENDB BRGH TRMT TX9D
55
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16
—
WUE ABDEN
55
SPBRGH EUSART Baud Rate Generator Register High Byte
55
SPBRG EUSART Baud Rate Generator Register Low Byte
55
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.
Note 1: Reserved in 28-pin devices; always maintain these bits clear.
DS39632E-page 262
© 2009 Microchip Technology Inc.