Maxim Integrated High-Speed Microcontroller Users Guide: DS80C390 Supplement - Manual (Page 28)

High-Speed Microcontroller User’s Guide: DS80C390 Supplement
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SERIAL PORT 0 CONTROL (SCON0)
7 6 5 4 3 2 1 0
SFR 98h SM0/FE_0 SM1_0 SM2_0 REN_0 TB8_0 RB8_0 T1_0 R1_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
SM0-2
Bits 7-5 Serial Port Mode. These bits control the mode of serial port 0. In addition the
SM0 and SM2_0 bits have secondary functions as shown below.
SM0 SM1 SM2 MODE FUNCTION LENGTH PERIOD
0 0 0 0 Synchronous 8 bits 12 t
CLK
0 0 1 0 Synchronous 8 bits 4 t
CLK
0 1 X 1 Asynchronous 10 bits
Timer 1 or 2
baud rate equation
1 0 0 2 Asynchronous 11 bits 64 t CLK
(SMOD=0)
32 t
CLK
(SMOD=1)
1 0 1 2
Asynchronous w/
Multiprocessor communication
11 bits
64 t
CLK
(SMOD=0)
32 t
CLK
(SMOD=1)
1 1 0 3 Asynchronous 11 bits
Timer 1 or 2
baud rate equation
1 1 1 3
Asynchronous w/
Multiprocessor communication
11 bits Timer 1 or 2
baud rate equation
SM0/FE_0
Bit 7 Framing Error Flag. When SMOD0 (PCON.6)=0, this bit (SM0) is used to
select the mode for serial port 0. When SMOD0 (PCON.6)=1, this bit (FE) will
be set upon detection of an invalid stop bit. When used as FE, this bit must be
cleared in software. Once the SMOD0 bit is set, modifications to this bit will not
affect the serial port mode settings. Although accessed from the same register,
internally the data for bits SM0 and FE are stored in different locations.
SM1_0
Bit 6 No alternate function.
SM2_0
Bit 5 Multiple CPU Communications. The function of this bit is dependent on the
serial port 0 mode.
Mode 0: Selects 12 t
CLK
or 4 t
CLK
period for synchronous serial port 0 data
transfers.
Mode 1: When set, reception is ignored (RI_0 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_0 bit from being set, and an
interrupt being asserted, if the 9
th bit received is not 1.
REN_0
Bit 4 Receiver Enable. This bit enable/disables the serial port 0 receiver shift register.
0 = Serial port 0 reception disabled.
1= Serial port 0 receiver enabled (modes 1, 2, 3). Initiate synchronous reception
(mode 0).