PIC24HJ12GP201 Datasheet, PDF (147/234 Pages) Microchip Technology – High-Performance, 16-Bit Microcontrollers

PIC24HJ12GP201/202
16.2 Transmitting in 8-bit Data Mode
1. Set up the UART:
a) Write appropriate values for data, parity and
Stop bits.
b) Write appropriate baud rate value to the
BRGx register.
c) Set up transmit and receive interrupt enable
and priority bits.
2. Enable the UART.
3. Set the UTXEN bit (causes a transmit interrupt).
4. Write data byte to lower byte of UxTXREG word.
The value will be immediately transferred to the
Transmit Shift Register (TSR) and the serial bit
stream will start shifting out with the next rising
edge of the baud clock.
Alternately, the data byte can be transferred
while UTXEN = 0, and the user application can
set UTXEN. This causes the serial bit stream to
begin immediately, because the baud clock
starts from a cleared state.
A transmit interrupt will be generated as per interrupt
control bits, UTXISEL<1:0>.
16.3 Transmitting in 9-bit Data Mode
1. Set up the UART (as described in Section 16.2
“Transmitting in 8-bit Data Mode”).
2. Enable the UART.
3. Set the UTXEN bit (causes a transmit interrupt).
4. Write UxTXREG as a 16-bit value only.
5. A word write to UxTXREG triggers the transfer
of the 9-bit data to the TSR. The serial bit stream
will start shifting out with the first rising edge of
the baud clock.
A transmit interrupt will be generated as per the setting
of control bits, UTXISEL<1:0>.
16.4 Break and Sync Transmit
Sequence
The following sequence will send a message frame
header made up of a Break, followed by an auto-baud
Sync byte.
1. Configure the UART for the desired mode.
2. Set UTXEN and UTXBRK, which sets up the
Break character.
3. Load the UxTXREG register with a dummy
character to initiate transmission (value is
ignored).
4. Write 0x55 to UxTXREG, which loads the Sync
character into the transmit FIFO. After the Break
has been sent, the UTXBRK bit is reset by
hardware.
The Sync character now transmits.
16.5 Receiving in 8-bit or 9-bit Data
Mode
1. Set up the UART (as described in Section 16.2
“Transmitting in 8-bit Data Mode”).
2. Enable the UART. A receive interrupt will be
generated when one or more data characters
have been received as per interrupt control bits,
URXISEL<1:0>.
3. Read the OERR bit to determine if an overrun
error has occurred. The OERR bit must be reset
in software.
4. Read UxRXREG.
The act of reading the UxRXREG character will move
the next character to the top of the receive FIFO,
including a new set of PERR and FERR values.
16.6 Flow Control Using UxCTS and
UxRTS Pins
UARTx Clear to Send (UxCTS) and Request to Send
(UxRTS) are the two hardware controlled active-low
pins associated with the UART module. The UEN<1:0>
bits in the UxMODE register configure these pins.
These two pins allow the UART to operate in Simplex
and Flow Control modes. They are implemented to
control the transmission and the reception between the
Data Terminal Equipment (DTE).
16.7 Infrared Support
The UART module provides two types of infrared UART
support:
• IrDA clock output to support external IrDA
encoder and decoder device (legacy module
support)
• Full implementation of the IrDA encoder and
decoder.
16.7.1 EXTERNAL IrDA SUPPORT – IrDA
CLOCK OUTPUT
To support external IrDA encoder and decoder devices,
the BCLK pin can be configured to generate the 16x
baud clock. With UEN<1:0> = 11, the BCLK pin will
output the 16x baud clock if the UART module is
enabled. The pin can be used to support the IrDA
codec chip.
16.7.2 BUILT-IN IrDA ENCODER AND
DECODER
The UART module includes full implementation of the
IrDA encoder and decoder. The built-in IrDA encoder
and decoder functionality is enabled using the IREN bit
(UxMODE<12>). When enabled (IREN = 1), the
receive pin (UxRX) acts as the input from the infrared
receiver. The transmit pin (UxTX) acts as the output to
the infrared transmitter.
© 2007 Microchip Technology Inc.
Preliminary
DS70282B-page 145