C8051F015DK Silicon Laboratories Inc, C8051F015DK Datasheet - Page 134

• Manufacturer Part Number: C8051F015DK
• Description: MCU, MPU & DSP Development Tools Dev Kit for F015-19
• Manufacturer: Silicon Laboratories Inc

Specifications of C8051F015DK

• Processor To Be Evaluated: C8051F01x
• Interface Type: USB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

18.1.3. Mode 2: 9-Bit UART, Fixed Baud Rate
Mode 2 provides asynchronous, full-duplex communication using a total of eleven bits per data byte: a start bit, 8
data bits (LSB first), a programmable ninth data bit, and a stop bit (see timing diagram in Figure 18.6). On transmit,
the ninth data bit is determined by the value in TB8 (SCON.3). It can be assigned the value of the parity flag P in
the PSW or used in multiprocessor communications. On receive, the ninth data bit goes into RB8 (SCON.2) and the
stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF register. The TI Transmit Interrupt
Flag (SCON.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin
any time after the REN Receive Enable bit (SCON.4) is set to logic 1. After the stop bit is received, the data byte
will be loaded into the SBUF receive register if the following conditions are met: RI must be logic 0, and if SM2 is
logic 1, the 9
If these conditions are met, the eight bits of data are stored in SBUF, the ninth bit is stored in RB8 and the RI flag is
set. If these conditions are not met, SBUF and RB8 will not be loaded and the RI flag will not be set. An interrupt
will occur if enabled when either TI or RI are set.
The baud rate in Mode 2 is a direct function of the system clock frequency as follows:
The SMOD bit (PCON.7) selects whether to divide SYSCLK by 32 or 64. In the formula, 2 is raised to the power
SMOD, resulting in a baud rate of either 1/32 or 1/64 of the system clock frequency. On reset, the SMOD bit is
logic 0, thus selecting the lower speed baud rate by default.
18.1.4. Mode 3: 9-Bit UART, Variable Baud Rate
Mode 3 is the same as Mode 2 in all respects except the baud rate is variable. The baud rate is determined in the
same manner as for Mode 1. Mode 3 operation transmits 11 bits: a start bit, 8 data bits (LSB first), a programmable
ninth data bit, and a stop bit. Timer 1 or Timer 2 overflows generate the baud rate just as with Mode 1. In
summary, Mode 3 transmits using the same protocol as Mode 2 but with Mode 1 baud rate generation.
SPACE
MARK
BIT TIMES
BIT SAMPLING
th
bit must be logic 1.
START
BIT
Figure 18.6. UART Modes 2 and 3 Timing Diagram
D0
D1
Mode 2 Baud Rate = 2
D2
Rev. 1.7
D3
SMOD
D4
* (SYSCLK / 64).
D5
C8051F000/1/2/5/6/7
C8051F010/1/2/5/6/7
D6
D7
D8
STOP
BIT
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