PIC18LF24K Datasheet, PDF (392/594 Pages) –

PIC18(L)F26/45/46K40
27.2.1.5 TSR Status
The TRMT bit of the TXxSTA register indicates the
status of the TSR register. This is a read-only bit. The
TRMT bit is set when the TSR register is empty and is
cleared when a character is transferred to the TSR
register from the TXxREG. The TRMT bit remains clear
until all bits have been shifted out of the TSR register.
No interrupt logic is tied to this bit, so the user has to
poll this bit to determine the TSR status.
Note: The TSR register is not mapped in data
memory, so it is not available to the user.
27.2.1.6 Transmitting 9-Bit Characters
The EUSART supports 9-bit character transmissions.
When the TX9 bit of the TXxSTA register is set, the
EUSART will shift nine bits out for each character trans-
mitted. The TX9D bit of the TXxSTA register is the
ninth, and Most Significant data bit. When transmitting
9-bit data, the TX9D data bit must be written before
writing the eight Least Significant bits into the TXxREG.
All nine bits of data will be transferred to the TSR shift
register immediately after the TXxREG is written.
A special 9-bit Address mode is available for use with
multiple receivers. See Section 27.2.2.7 “Address
Detection” for more information on the Address mode.
27.2.1.7 Asynchronous Transmission Setup:
1. Initialize the SPxBRGH, SPxBRGL register pair
and the BRGH and BRG16 bits to achieve the
desired baud rate (see Section 27.4 “EUSART
Baud Rate Generator (BRG)”).
2. Enable the asynchronous serial port by clearing
the SYNC bit and setting the SPEN bit.
3. If 9-bit transmission is desired, set the TX9
control bit. A set ninth data bit will indicate that
the eight Least Significant data bits are an
address when the receiver is set for address
detection.
4. Set SCKP bit if inverted transmit is desired.
5. Enable the transmission by setting the TXEN
control bit. This will cause the TXxIF interrupt bit
to be set.
6. If interrupts are desired, set the TXxIE interrupt
enable bit of the PIE3 register. An interrupt will
occur immediately provided that the GIE and
PEIE bits of the INTCON register are also set.
7. If 9-bit transmission is selected, the ninth bit
should be loaded into the TX9D data bit.
8. Load 8-bit data into the TXxREG register. This
will start the transmission.
FIGURE 27-3:
ASYNCHRONOUS TRANSMISSION
Write to TXxREG
BRG Output
(Shift Clock)
TXx/CKx
pin
TXxIF bit
(Transmit Buffer
Reg. Empty Flag)
Word 1
Start bit
bit 0
1 TCY
bit 1
Word 1
bit 7/8 _{Stop bit}
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Word 1
Transmit Shift Reg.
 2016 Microchip Technology Inc.
Preliminary
DS40001816C-page 392