C8051F317-GMR Silicon Laboratories Inc, C8051F317-GMR Datasheet - Page 164

• Manufacturer Part Number: C8051F317-GMR
• Description: MCU 8-Bit C8051F31x 8051 CISC 16KB Flash 3.3V 24-Pin QFN EP T/R
• Manufacturer: Silicon Laboratories Inc

Specifications of C8051F317-GMR

• Package: 24QFN EP
• Device Core: 8051
• Family Name: C8051F31x
• Maximum Speed: 25 MHz
• Ram Size: 1.25 KB
• Program Memory Size: 16 KB
• Operating Supply Voltage: 3.3 V
• Data Bus Width: 8 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 21
• Interface Type: I2C/SMBus/SPI/UART
• On-chip Adc: 17-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 4

C8051F310/1/2/3/4/5/6/7
15.1. Enhanced Baud Rate Generation
The UART0 baud rate is generated by Timer 1 in 8-bit auto-reload mode. The TX clock is generated by
TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure 15.2), which is not user-
accessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates.
The RX Timer runs when Timer 1 is enabled, and uses the same reload value (TH1). However, an
RX Timer reload is forced when a START condition is detected on the RX pin. This allows a receive to
begin any time a START is detected, independent of the TX Timer state.
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see
ter/Timer with Auto-Reload” on page
occur at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by one of six
sources: SYSCLK, SYSCLK / 4, SYSCLK / 12, SYSCLK / 48, the external oscillator clock / 8, or an exter-
nal input T1. For any given Timer 1 clock source, the UART0 baud rate is determined by Equation 15.1.
Where T1
value). Timer 1 clock frequency is selected as described in
reference for typical baud rates and system clock frequencies is given in Table 15.1 through Table 15.6.
Note that the internal oscillator may still generate the system clock when the external oscillator is driving
Timer 1.
164
CLK
is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (reload
Detected
Start
Figure 15.2. UART0 Baud Rate Logic
RX Timer
Equation 15.1. UART0 Baud Rate
UartBaudRate
Timer 1
TH1
TL1
189). The Timer 1 reload value should be set so that overflows will
Overflow
Overflow
Rev. 1.7
=
------------------------------ -

256 T1H
T1
–
Section “17. Timers” on page
CLK
2
2
Section “17.1.3. Mode 2: 8-bit Coun-


UART
1
-- -
2
RX Clock
TX Clock
187. A quick