Maxim Integrated High-Speed Microcontroller - Manual (Page 41)

High-Speed Microcontroller User’s Guide
Rev: 062210 41 of 176
SM2_1
Bit 5 Multiple CPU Communications. The function of this bit is dependent on the serial port 1
mode.
Mode 0: Selects 12t
CLK
or 4t
CLK
period for synchronous port 1 data transfers.
Mode 1: When this bit is 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 mode 2 and 3.
This will prevent RI_1 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 Receiver 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.
4.2.30 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–SBUF1.0
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.