
PIC18F1230/1330
DS39758D-page 166
2009 Microchip Technology Inc.
15.3.2
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.
If any error occurred, clear the error by clearing
bit, CREN.
2.
If using interrupts, ensure that the GIE and PEIE bits
in the INTCON register (INTCON<7:6>) are set.
3.
Initialize the SPBRGH:SPBRG registers for the
appropriate baud rate. Set or clear the BRG16
bit, as required, to achieve the desired baud
rate.
4.
Enable the synchronous master serial port by
setting bits, SYNC, SPEN and CSRC.
5.
Ensure bits, CREN and SREN, are clear.
6.
If the signal from the CK pin is to be inverted, set
the TXCKP bit.
7.
If interrupts are desired, set enable bit, RCIE.
8.
If 9-bit reception is desired, set bit, RX9.
9.
If a single reception is required, set bit, SREN.
For continuous reception, set bit, CREN.
10. Interrupt flag bit, RCIF, will be set when reception
is complete and an interrupt will be generated if
the enable bit, RCIE, was set.
11. Read the RCSTA register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
12. Read the 8-bit received data by reading the
RCREG register.
FIGURE 15-13:
SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
TABLE 15-8:
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
PIR1
—
ADIF
RCIF
TXIF
CMP2IF
CMP1IF
CMP0IF
TMR1IF
PIE1
—
ADIE
RCIE
TXIE
CMP2IE
CMP1IE
CMP0IE
TMR1IE
IPR1
—
ADIP
RCIP
TXIP
CMP2IP
CMP1IP
CMP0IP
TMR1IP
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
RCREG
EUSART Receive Register
TXSTA
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
BAUDCON ABDOVF
RCIDL
RXDTP
TXCKP
BRG16
—
WUE
ABDEN
SPBRGH
EUSART Baud Rate Generator Register High Byte
SPBRG
EUSART Baud Rate Generator Register Low Byte
Legend:
— = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.
CREN bit
RA3/RX/DT
RA2/TX/CK pin
Write to
bit SREN
SREN bit
RCIF bit
(Interrupt)
Read
RXREG
Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Q2
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
‘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.
pin
(TXCKP)