PIC18F-LF1XK50 MICROCHIP [Microchip Technology], PIC18F-LF1XK50 Datasheet - Page 184

• Manufacturer Part Number: PIC18F-LF1XK50
• Description: 20-Pin USB Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F/LF1XK50
16.1.1.4
The TXIF interrupt flag bit of the PIR1 register is set
whenever the EUSART transmitter is enabled and no
character is being held for transmission in the TXREG.
In other words, the TXIF bit is only clear when the TSR
is busy with a character and a new character has been
queued for transmission in the TXREG. The TXIF flag bit
is not cleared immediately upon writing TXREG. TXIF
becomes valid in the second instruction cycle following
the write execution. Polling TXIF immediately following
the TXREG write will return invalid results. The TXIF bit
is read-only, it cannot be set or cleared by software.
The TXIF interrupt can be enabled by setting the TXIE
interrupt enable bit of the PIE1 register. However, the
TXIF flag bit will be set whenever the TXREG is empty,
regardless of the state of TXIE enable bit.
To use interrupts when transmitting data, set the TXIE
bit only when there is more data to send. Clear the
TXIE interrupt enable bit upon writing the last character
of the transmission to the TXREG.
16.1.1.5
The TRMT bit of the TXSTA 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 TXREG. 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 needs to
poll this bit to determine the TSR status.
DS41350E-page 184
Note:
The TSR register is not mapped in data
memory, so it is not available to the user.
Transmit Interrupt Flag
TSR Status
Preliminary
16.1.1.6
The EUSART supports 9-bit character transmissions.
When the TX9 bit of the TXSTA register is set the
EUSART will shift 9 bits out for each character transmit-
ted. The TX9D bit of the TXSTA register is the ninth,
and Most Significant, data bit. When transmitting 9-bit
data, the TX9D data bit must be written before writing
the 8 Least Significant bits into the TXREG. All nine bits
of data will be transferred to the TSR shift register
immediately after the TXREG is written.
A special 9-bit Address mode is available for use with
multiple receivers. See
Detection”
16.1.1.7
1.
2.
3.
4.
5.
6.
7.
8.
Initialize the SPBRGH:SPBRG register pair and
the BRGH and BRG16 bits to achieve the desired
baud rate (see
Rate Generator
Enable the asynchronous serial port by clearing
the SYNC bit and setting the SPEN bit.
If 9-bit transmission is desired, set the TX9 con-
trol bit. A set ninth data bit will indicate that the 8
Least Significant data bits are an address when
the receiver is set for address detection.
Set the CKTXP control bit if inverted transmit
data polarity is desired.
Enable the transmission by setting the TXEN
control bit. This will cause the TXIF interrupt bit
to be set.
If interrupts are desired, set the TXIE interrupt
enable bit. An interrupt will occur immediately
provided that the GIE and PEIE bits of the
INTCON register are also set.
If 9-bit transmission is selected, the ninth bit
should be loaded into the TX9D data bit.
Load 8-bit data into the TXREG register. This
will start the transmission.
for more information on the Address mode.
Transmitting 9-Bit Characters
Asynchronous Transmission Set-up:
Section 16.3 “EUSART Baud
(BRG)”).
 2010 Microchip Technology Inc.
Section 16.1.2.8 “Address