PIC16F720_13 Datasheet, PDF (134/254 Pages) Microchip Technology – 20-Pin Flash Microcontrollers

PIC16(L)F720/721
16.3.2 SYNCHRONOUS SLAVE MODE
The following bits are used to configure the AUSART
for synchronous slave operation:
• SYNC = 1
• CSRC = 0
• SREN = 0 (for transmit); SREN = 1 (for receive)
• CREN = 0 (for transmit); CREN = 1 (for receive)
• SPEN = 1
Setting the SYNC bit of the TXSTA register configures the
device for synchronous operation. Clearing the CSRC bit
of the TXSTA register configures the device as a slave.
Clearing the SREN and CREN bits of the RCSTA register
ensures that the device is in the Transmit mode,
otherwise the device will be configured to receive. Setting
the SPEN bit of the RCSTA register enables the
AUSART.
16.3.2.1 AUSART Synchronous Slave
Transmit
The operation of the Synchronous Master and Slave
modes are identical (refer to Section 16.3.1.2
“Synchronous Master Transmission”), except in the
case of the Sleep mode.
If two words are written to the TXREG and then the
SLEEP instruction is executed, the following will occur:
1. The first character will immediately transfer to
the TSR register and transmit.
2. The second word will remain in TXREG register.
3. The TXIF bit will not be set.
4. After the first character has been shifted out of
TSR, the TXREG register will transfer the second
character to the TSR and the TXIF bit will now be
set.
5. If the PEIE and TXIE bits are set, the interrupt
will wake the device from Sleep and execute the
next instruction. If the GIE bit is also set, the
program will call the Interrupt Service Routine.
16.3.2.2 Synchronous Slave Transmission
Setup
1. Set the SYNC and SPEN bits and clear the
CSRC bit.
2. Clear the CREN and SREN bits.
3. If using interrupts, ensure that the GIE and PEIE
bits of the INTCON register are set and set the
TXIE bit.
4. If 9-bit transmission is desired, set the TX9 bit.
5. Enable transmission by setting the TXEN bit.
6. Verify address detection is disabled by clearing
the ADDEN bit of the RCSTA register.
7. If 9-bit transmission is selected, insert the Most
Significant bit into the TX9D bit.
8. Start transmission by writing the Least
Significant 8 bits to the TXREG register.
TABLE 16-8: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Register
on Page
INTCON
GIE
PEIE TMR0IE INTE RABIE TMR0IF INTF RABIF
38
PIE1
TMR1GIE ADIE
RCIE
TXIE SSPIE CCP1IE TMR2IE TMR1IE
39
PIR1
TMR1GIF ADIF
RCIF
TXIF SSPIF CCP1IF TMR2IF TMR1IF
40
RCSTA
SPEN
RX9
SREN CREN ADDEN FERR OERR RX9D
126
TRISC
TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0
61
TXREG
AUSART Transmit Data Register
—
TXSTA
CSRC
TX9
TXEN SYNC
—
BRGH TRMT TX9D
125
Legend: x = unknown, - = unimplemented read as ‘0’. Shaded cells are not used for synchronous slave
transmission.
DS41430D-page 134
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