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PIC18F2450/4450
DS39760A-page 170
Advance Information
2006 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.
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 interrupts are desired, set enable bit RCIE.
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 RCIF will be set when reception
is complete and an interrupt will be generated if
the enable bit RCIE was set.
8.
Read the RCSTA register to get the ninth bit (if
enabled) and determine if any error occurred
during reception.
9.
Read the 8-bit received data by reading the
RCREG 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 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
—
CCP1IF
TMR2IF
TMR1IF
PIE1
—
ADIE
RCIE
TXIE
—
CCP1IE
TMR2IE
TMR1IE
IPR1
—
ADIP
RCIP
TXIP
—
CCP1IP
TMR2IP
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
—
SCKP
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
RC7/RX/DT
RC6/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.
RC6/TX/CK pin
pin
(SCKP = 0)
(SCKP = 1)