PIC18F2450/4450
To set up a Synchronous Slave Transmission:
15.4 EUSART Synchronous
Slave Mode
1. Enable the synchronous slave serial port by
setting bits SYNC and SPEN and clearing bit
CSRC.
Synchronous Slave mode is entered by clearing bit,
CSRC (TXSTA<7>). This mode differs from the
Synchronous Master mode in that the shift clock is
supplied externally at the CK pin (instead of being
supplied internally in Master mode). This allows the
device to transfer or receive data while in any low-power
mode.
2. Clear bits CREN and SREN.
3. If interrupts are desired, set enable bit TXIE.
4. If 9-bit transmission is desired, set bit TX9.
5. Enable the transmission by setting enable bit
TXEN.
6. If 9-bit transmission is selected, the ninth bit
should be loaded in bit TX9D.
15.4.1
EUSART SYNCHRONOUS
SLAVE TRANSMIT
7. Start transmission by loading data to the TXREG
register.
The operation of the Synchronous Master and Slave
modes is identical, except in the case of Sleep mode.
8. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
If two words are written to the TXREG register and then
the SLEEPinstruction is executed, the following will occur:
a) The first word will immediately transfer to the
TSR register and transmit.
b) The second word will remain in the TXREG
register.
c) Flag bit TXIF will not be set.
d) When the first word has been shifted out of TSR,
the TXREG register will transfer the second word
to the TSR and flag bit TXIF will now be set.
e) If enable bit TXIE is set, the interrupt will wake the
chip from Sleep. If the global interrupt is enabled,
the program will branch to the interrupt vector.
TABLE 15-9: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION
Reset
Values
on page
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
INTCON
PIR1
GIE/GIEH PEIE/GIEL TMR0IE
INT0IE
TXIF
RBIE
—
TMR0IF
CCP1IF
CCP1IE
CCP1IP
FERR
INT0IF
RBIF
49
51
51
51
51
50
51
51
50
50
—
—
ADIF
ADIE
ADIP
RX9
RCIF
RCIE
RCIP
SREN
TMR2IF
TMR1IF
PIE1
TXIE
—
TMR2IE TMR1IE
TMR2IP TMR1IP
IPR1
—
TXIP
—
RCSTA
TXREG
TXSTA
SPEN
CREN
ADDEN
OERR
RX9D
EUSART Transmit Register
CSRC
TX9
TXEN
—
SYNC
SCKP
SENDB
BRG16
BRGH
—
TRMT
WUE
TX9D
BAUDCON ABDOVF
RCIDL
ABDEN
SPBRGH
SPBRG
EUSART Baud Rate Generator Register High Byte
EUSART Baud Rate Generator Register Low Byte
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave transmission.
© 2006 Microchip Technology Inc.
Advance Information
DS39760A-page 171
MICROCHIP [ MICROCHIP ]
