C8051F557-IM Silicon Laboratories Inc, C8051F557-IM Datasheet - Page 233
![IC 8051 MCU 16K FLASH 24-QFN](/photos/12/15/121587/c8051f9xx_24-qfn_sml.jpg)
C8051F557-IM
Manufacturer Part Number
C8051F557-IM
Description
IC 8051 MCU 16K FLASH 24-QFN
Manufacturer
Silicon Laboratories Inc
Series
C8051F55xr
Specifications of C8051F557-IM
Program Memory Type
FLASH
Program Memory Size
16KB (16K x 8)
Package / Case
24-QFN
Core Processor
8051
Core Size
8-Bit
Speed
50MHz
Connectivity
SMBus (2-Wire/I²C), SPI, UART/USART
Peripherals
POR, PWM, Temp Sensor, WDT
Number Of I /o
18
Ram Size
2.25K x 8
Voltage - Supply (vcc/vdd)
1.8 V ~ 5.25 V
Data Converters
A/D 18x12b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 125°C
Processor Series
C8051F5x
Core
8051
Data Bus Width
8 bit
Data Ram Size
2304 B
Maximum Clock Frequency
50 MHz
Number Of Programmable I/os
18
Operating Supply Voltage
1.8 V to 5.25 V
Maximum Operating Temperature
+ 125 C
Mounting Style
SMD/SMT
3rd Party Development Tools
PK51, CA51, A51, ULINK2
Development Tools By Supplier
C8051F540DK
Minimum Operating Temperature
- 40 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
For Use With
336-1691 - KIT DEVELOPMENT FOR C8051F560
Eeprom Size
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
Other names
336-1690-5
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23. UART0
UART0 is an asynchronous, full duplex serial port offering a variety of data formatting options. A dedicated
baud rate generator with a 16-bit timer and selectable prescaler is included, which can generate a wide
range of baud rates (details in Section “23.1. Baud Rate Generator” on page 233). A received data FIFO
allows UART0 to receive up to three data bytes before data is lost and an overflow occurs.
UART0 has six associated SFRs. Three are used for the Baud Rate Generator (SBCON0, SBRLH0, and
SBRLL0), two are used for data formatting, control, and status functions (SCON0, SMOD0), and one is
used to send and receive data (SBUF0). The single SBUF0 location provides access to both the transmit
holding register and the receive FIFO. Writes to SBUF0 always access the Transmit register. Reads of
SBUF0 always access the first byte of the Receive FIFO; it is not possible to read data from the
Transmit Holding Register.
With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in
SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not
cleared by hardware when the CPU vectors to the interrupt service routine. They must be cleared manually
by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive
complete). If additional bytes are available in the Receive FIFO, the RI0 bit cannot be cleared by software.
23.1. Baud Rate Generator
The UART0 baud rate is generated by a dedicated 16-bit timer which runs from the controller’s core clock
(SYSCLK) and has prescaler options of 1, 4, 12, or 48. The timer and prescaler options combined allow for
a wide selection of baud rates over many clock frequencies.
The baud rate generator is configured using three registers: SBCON0, SBRLH0, and SBRLL0. The
UART0 Baud Rate Generator Control Register (SBCON0, SFR Definition 23.4) enables or disables the
baud rate generator and selects the prescaler value for the timer. The baud rate generator must be
enabled for UART0 to function. Registers SBRLH0 and SBRLL0 contain a 16-bit reload value for the dedi-
cated 16-bit timer. The internal timer counts up from the reload value on every clock tick. On timer over-
flows (0xFFFF to 0x0000), the timer is reloaded. The baud rate for UART0 is defined in Equation 23.1,
where “BRG Clock” is the baud rate generator’s selected clock source. For reliable UART operation, it is
recommended that the UART baud rate is not configured for baud rates faster than SYSCLK/16.
SYSCLK
SBRLH0
Timer (16-bit)
Baud Rate Generator
SBRLL0
EN
SBCON0
Figure 23.1. UART0 Block Diagram
Overflow
(1, 4, 12, 48)
Pre-Scaler
Rev. 1.1
Data Formatting
Control / Status
Interrupt
UART0
SMOD0
SCON0
C8051F55x/56x/57x
TX Holding
RX FIFO
(3 Deep)
Register
SBUF0
Logic
Logic
RX
TX
Write to SBUF0
Read of SBUF0
TX0
RX0
233
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