C8051F131R Silicon Labs, C8051F131R Datasheet - Page 300

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C8051F131R

Manufacturer Part Number
C8051F131R
Description
8-bit Microcontrollers - MCU 128kB 100MIPS 8448B RAM
Manufacturer
Silicon Labs
Datasheet

Specifications of C8051F131R

Product Category
8-bit Microcontrollers - MCU
Core
8051
Data Bus Width
8 bit
Maximum Clock Frequency
100 MHz
Program Memory Size
128 KB
Data Ram Size
8.25 KB
On-chip Adc
Yes
Operating Supply Voltage
2.7 V to 3.6 V
Package / Case
TQFP-64
Mounting Style
SMD/SMT
A/d Bit Size
10 bit
A/d Channels Available
9
Data Rom Size
64 KB
Interface Type
I2C, SMBus, SPI, UART
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 40 C
Number Of Programmable I/os
32
Number Of Timers
16 bit
Processor Series
C8051
Program Memory Type
Flash
Factory Pack Quantity
500
Supply Voltage - Max
3.6 V
Supply Voltage - Min
3 V
C8051F120/1/2/3/4/5/6/7
C8051F130/1/2/3
22.1. Enhanced Baud Rate Generation
The UART1 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 22.2), 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
Timer with Auto-Reload” on page 311
occur at two times the desired baud rate. Note that Timer 1 may be clocked by one of five sources: SYS-
CLK, SYSCLK / 4, SYSCLK / 12, SYSCLK / 48, or the external oscillator clock / 8. For any given Timer 1
clock source, the UART1 baud rate is determined by Equation 22.1.
Where T1
value). Timer 1 clock frequency is selected as described in
page 309
through Table 22.5. Note that the internal oscillator or PLL may still generate the system clock when the
external oscillator is driving Timer 1 (see
details).
300
. A quick reference for typical baud rates and system clock frequencies is given in Table 22.1
CLK
is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (reload
Detected
Start
Figure 22.2. UART1 Baud Rate Logic
RX Timer
Equation 22.1. UART1 Baud Rate
UARTBaudRate
Timer 1
TH1
TL1
). The Timer 1 reload value should be set so that overflows will
Section “23.1. Timer 0 and Timer 1” on page 309
Overflow
Overflow
Rev. 1.4
=
------------------------------ -
256 T1H
T1
CLK
Section “23.1. Timer 0 and Timer 1” on
Section “23.1.3. Mode 2: 8-bit Counter/
2
2
UART1
1
-- -
2
RX Clock
TX Clock
for more

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