Datasheet

© 2011 Microchip Technology Inc. DS70143E-page 107
dsPIC30F6011A/6012A/6013A/6014A
16.5.2 FRAMING ERROR (FERR)
The FERR bit (UxSTA<2>) is set if a ‘0’ is detected
instead of a Stop bit. If two Stop bits are selected, both
Stop bits must be ‘1’, otherwise FERR will be set. The
read only FERR bit is buffered along with the received
data. It is cleared on any Reset.
16.5.3 PARITY ERROR (PERR)
The PERR bit (UxSTA<3>) is set if the parity of the
received word is incorrect. This error bit is applicable
only if a Parity mode (odd or even) is selected. The
read only PERR bit is buffered along with the received
data bytes. It is cleared on any Reset.
16.5.4 IDLE STATUS
When the receiver is active (i.e., between the initial
detection of the Start bit and the completion of the Stop
bit), the RIDLE bit (UxSTA<4>) is ‘0’. Between the com-
pletion of the Stop bit and detection of the next Start bit,
the RIDLE bit is ‘1’, indicating that the UART is Idle.
16.5.5 RECEIVE BREAK
The receiver will count and expect a certain number of
bit times based on the values programmed in the
PDSEL (UxMODE<2:1>) and STSEL (UxMODE<0>)
bits.
If the break is longer than 13 bit times, the reception is
considered complete after the number of bit times
specified by PDSEL and STSEL. The URXDA bit is set,
FERR is set, zeros are loaded into the receive FIFO,
interrupts are generated if appropriate and the RIDLE
bit is set.
When the module receives a long break signal and the
receiver has detected the Start bit, the data bits and the
invalid Stop bit (which sets the FERR), the receiver
must wait for a valid Stop bit before looking for the next
Start bit. It cannot assume that the break condition on
the line is the next Start bit.
Break is regarded as a character containing all ‘0’s with
the FERR bit set. The break character is loaded into the
buffer. No further reception can occur until a Stop bit is
received. Note that RIDLE goes high when the Stop bit
has not yet been received.
16.6 Address Detect Mode
Setting the ADDEN bit (UxSTA<5>) enables this spe-
cial mode in which a 9th bit (URX8) value of ‘1’ identi-
fies the received word as an address, rather than data.
This mode is only applicable for 9-bit data communica-
tion. The URXISEL control bit does not have any
impact on interrupt generation in this mode since an
interrupt (if enabled) will be generated every time the
received word has the 9th bit set.
16.7 Loopback Mode
Setting the LPBACK bit enables this special mode in
which the UxTX pin is internally connected to the UxRX
pin. When configured for the Loopback mode, the
UxRX pin is disconnected from the internal UART
receive logic. However, the UxTX pin still functions as
in a normal operation.
To select this mode:
1. Configure UART for desired mode of operation.
2. Set LPBACK = 1 to enable Loopback mode.
3. Enable transmission as defined in Section 16.3
“Transmitting Data”.
16.8 Baud Rate Generator
The UART has a 16-bit Baud Rate Generator to allow
maximum flexibility in baud rate generation. The Baud
Rate Generator register (UxBRG) is readable and
writable. The baud rate is computed as shown in
Equation 16-1:
EQUATION 16-1: BAUD RATE
Where:
BRG = 16-bit value held in UxBRG register
(0 through 65535)
F
CY = Instruction Clock Rate (1/TCY)
Therefore, the maximum baud rate possible is:
F
CY/16 (if BRG = 0),
and the minimum baud rate possible is:
F
CY/(16 * 65536).
With a full 16-bit Baud Rate Generator at 30 MIPS
operation, the minimum baud rate achievable is
28.5 bps.
Baud Rate = FCY/(16 * (BRG + 1))