Maxim Integrated High-Speed Microcontroller Users Guide: DS80C390 Supplement - Manual (Page 56)

High-Speed Microcontroller User’s Guide: DS80C390 Supplement
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Mode 1: When set, reception is ignored (RI_1 is not set) if invalid stop bit
received.
Mode 2/3: When this bit is set, multiprocessor communications are enabled in
modes 2 and 3. This will prevent the RI_1 bit from being set, and an
interrupt being asserted, if the 9th bit received is not 1.
REN_1
Bit 4 Receive Enable. This bit enables/disables the serial port 1 receiver shift register.
0 = Serial port 1 reception disabled.
1 = Serial port 1 receiver enabled (modes 1, 2, 3). Initiate synchronous reception
(mode 0).
TB8_1
Bit 3 9th Transmission Bit State. This bit defines the state of the 9th transmission bit
in serial port 1 modes 2 and 3.
RB8_1
Bit 2 9th Received Bit State. This bit identifies the state for the 9th reception bit
received data in serial pot 1 modes 2 and 3. In serial port mode 1, when
SM2_1=0, RB8_1 is the state of the stop bit. RB8_1 is not used in mode 0.
TI_1
Bit 1 Transmitter Interrupt Flag. This bit indicates that data in the serial port 1
buffer has been completely shifted out. In serial port mode 0, TI_1 is set at the
end of the 8th data bit. In all other modes, this bit is set at the end of the last data
bit. This bit must be manually cleared by software.
RI_1
Bit 0 Transmitter Interrupt Flag. This bit indicates that a byte of data has been
received in the serial port 1 buffer. In serial port mode 1, RI_1 is set at the end of
the 8th bit. In serial port mode 1, RI_1 is set after the last sample of the incoming
stop bit subject to the state of SM2_1. In modes 2 and 3, RI_1 is set after the last
sample of RB8_1. This bit must be manually cleared by software.
SERIAL DATA BUFFER 1 (SBUF1)
7 6 5 4 3 2 1 0
SFR C1h SBUF1.7 SBUF1.6 SBUF1.5 SBUF1.4 SBUF1.3 SBUF1.2 SBUF1.1 SBUF1.0
RW-0 RW-0 RW-0 RW-0 RW-0 RW-0 RW-0 RW-0
R = Unrestricted Read, W = Unrestricted Write, -n = Value after Reset
SBUF1.7-0
Bits 7-0 Serial Data Buffer 1. Data for serial port 1 is read from or written to this
location. The serial transmit and receive buffers are separate registers, but both
are addressed at this location.