Intel 8XC196NP, 80C196NU, Microcontroller manual Spstatus, RPE/RB8 TXE

8XC196NP, 80C196NU USER’S MANUAL

SP_STATUS	Address:	1FB9H
	Reset State:	0BH

The serial port status (SP_STATUS) register contains bits that indicate the status of the serial port.

7

RPE/RB8 RI TI FE

0

TXE OE — —

Bit	Bit	Function
Number	Mnemonic
7	RPE/RB8	Received Parity Error/Received Bit 8
		RPE is set if parity is disabled (SP_CON.2 = 0) and the ninth data bit
		received is high.
		RB8 is set if parity is enabled (SP_CON.2 = 1) and a parity error
		occurred.
		Reading SP_STATUS clears this bit.
6	RI	Receive Interrupt
		This bit is set when the last data bit is sampled. Reading SP_STATUS
		clears this bit.
		This bit need not be clear for the serial port to receive data.
5	TI	Transmit Interrupt
		This bit is set at the beginning of the stop bit transmission. Reading
		SP_STATUS clears this bit.
4	FE	Framing Error
		This bit is set if a stop bit is not found within the appropriate period of
		time. Reading SP_STATUS clears this bit.
3	TXE	SBUF_TX Empty
		This bit is set if the transmit buffer is empty and ready to accept up to two
		bytes. It is cleared when a byte is written to SBUF_TX.
2	OE	Overrun Error
		This bit is set if data in the receive shift register is loaded into SBUF_RX
		before the previous bit is read. Reading SP_STATUS clears this bit.
1:0	—	Reserved. These bits are undefined.

Figure 8-8. Serial Port Status (SP_STATUS) Register

The receiver checks for a valid stop bit. Unless a stop bit is found within the appropriate time, the framing error (FE) bit in the SP_STATUS register is set. When the stop bit is detected, the data in the receive shift register is loaded into SBUF_RX and the receive interrupt (RI) flag is set. If this happens before the previous byte in SBUF_RX is read, the overrun error (OE) bit is set. SBUF_RX always contains the latest byte received; it is never a combination of the last two bytes.

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