Microchip Technology PIC12F1501, Manual

Page: 248 / 402

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2011-2015 Microchip Technology Inc. DS40001609E-page 249
PIC16(L)F1508/9
22.5.2 SYNCHRONOUS SLAVE MODE
The following bits are used to configure the EUSART
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
EUSART.
22.5.2.1 EUSART Synchronous Slave
Transmit
The operation of the Synchronous Master and Slave
modes are identical (see
Section22.5.1.3 “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 the 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.
22.5.2.2 Synchronous Slave Transmission
Set-up:
1. Set the SYNC and SPEN bits and clear the
CSRC bit.
2. Clear the ANSEL bit for the CK pin (if applicable).
3. Clear the CREN and SREN bits.
4. If interrupts are desired, set the TXIE bit of the
PIE1 register and the GIE and PEIE bits of the
INTCON register.
5. If 9-bit transmission is desired, set the TX9 bit.
6. Enable transmission by setting the TXEN bit.
7. If 9-bit transmission is selected, insert the Most
Significant bit into the TX9D bit.
8. Start transmission by writing the Least
Significant eight bits to the TXREG register.
TABLE 22-9: SUMMARY OF 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
BAUDCON ABDOVF RCIDL — SCKP BRG16 — WUE ABDEN
235
INTCON GIE PEIE TMR0IE INTE IOCIE TMR0IF INTF IOCIF
75
PIE1 TMR1GIE ADIE RCIE TXIE SSP1IE — TMR2IE TMR1IE
76
PIR1 TMR1GIF ADIF RCIF TXIF SSP1IF — TMR2IF TMR1IF
79
RCSTA SPEN
RX9 SREN CREN ADDEN FERR OERR RX9D
234
TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 113
TXREG EUSART Transmit Data Register
225 *
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D
233
Legend:
— = unimplemented location, read as ‘
0
’. Shaded cells are not used for synchronous slave transmission.
* Page provides register information.