34.20.7 UxFIFO

UART FIFO Status Register

Note:

The BSF instruction will not be used to set RXBE because doing so will clear a byte pending in the transmit shift register when the UxTXB register is empty. Instead, use the MOVWF instruction with a ‘0’ in the TXBE bit location.

Name:	UxFIFO
Address:	0x1BE,0x1D2


Bit	7	6	5	4	3	2	1	0
	TXWRE	STPMD	TXBE	TXBF	RXIDL	XON	RXBE	RXBF
Access	R/W/S	R/W	R/W/S/C	R/S/C	R/S/C	S/C	R/W/S/C	R/S/C
Reset	0	0	1	0	1	1	1	0

Bit 7 – TXWRE Transmit Write Error Status (must be cleared by software)

Value	Name	Description
1	MODE = LIN Host	UxP1L was written when a host process was active
1	MODE = LIN Client	UxTXB was written when UxP2 = `0` or more than UxP2 bytes have been written to UxTXB since last Break
1	MODE = Address detect	UxP1L was written before the previous data in UxP1L was transferred to TX shifter
1	MODE = All	A new byte was written to UxTXB when the output FIFO was full
0	MODE = All	No error

Bit 6 – STPMD Stop Bit Detection Mode

Value	Name	Description
1	STP = `11`	Assert UxRXIF at end of first Stop bit
1	STP ≠ `11`	Assert UxRXIF at end of last Stop bit
0	STP = `xx`	Assert UxRXIF in middle of first Stop bit

Bit 5 – TXBE Transmit Buffer Empty Status

Value	Description
1	Transmit buffer is empty. Setting this bit will clear the transmit buffer and output shift register.
0	Transmit buffer is not empty. Software cannot clear this bit.

Bit 4 – TXBF Transmit Buffer Full Status

Value	Description
1	Transmit buffer is full
0	Transmit buffer is not full

Bit 3 – RXIDL Receive Pin Idle Status

Value	Description
1	Receive pin is in Idle state
0	UART is receiving Start, Stop, Data, Auto-baud, or Break

Bit 2 – XON Software Flow Control Transmit Enable Status

Value	Description
1	Transmitter is enabled
0	Transmitter is disabled

Bit 1 – RXBE Receive Buffer Empty Status

Value	Description
1	Receive buffer is empty. Setting this bit will clear the RX buffer⁽¹⁾.
0	Receive buffer is not empty. Software cannot clear this bit.

Bit 0 – RXBF Receive Buffer Full Status

Value	Description
1	Receive buffer is full
0	Receive buffer is not full

The BSF instruction will not be used to set RXBE because doing so will clear a byte pending in the transmit shift register when the UxTXB register is empty. Instead, use the MOVWF instruction with a ‘0’ in the TXBE bit location.