Datasheet

Functional overview STM32F051x
24/105 Doc ID 022265 Rev 3
3.17 Universal synchronous/asynchronous receiver transmitters
(USART)
The device embeds up to two universal synchronous/asynchronous receiver transmitters
(USART1 and USART2), which communicate at speeds of up to 6 Mbit/s.
They provide hardware management of the CTS, RTS and RS485 DE signals,
multiprocessor communication mode, master synchronous communication and single-wire
half-duplex communication mode. The USART1 supports also SmartCard communication
(ISO 7816), IrDA SIR ENDEC, LIN Master/Slave capability, auto baud rate feature and has a
clock domain independent from the CPU clock, allowing the USART1 to wake up the MCU
from Stop mode.
The USART interfaces can be served by the DMA controller.
Refer to Ta ble 1 0 for the differences between USART1 and USART2.
3.18 Serial peripheral interface (SPI)/Inter-integrated sound
interfaces (I
2
S)
Up to two SPIs are able to communicate up to 18 Mbits/s in slave and master modes in full-
duplex and simplex communication modes. The 3-bit prescaler gives 8 master mode
frequencies and the frame size is configurable from 4 bits to 16 bits.
One standard I
2
S interface (multiplexed with SPI1) supporting four different audio standards
can operate as master or slave at simplex communication mode. It can be configured to
transfer 16 and 24 or 32 bits with16-bit or 32-bit data resolution and synchronized by a
specific signal. Audio sampling frequency from 8 kHz up to 192 kHz can be set by 8-bit
Table 10. STM32F051x USART implementation
USART modes/features
(1)
1. X = supported.
USART1 USART2
Hardware flow control for modem X X
Continuous communication using DMA X X
Multiprocessor communication X X
Synchronous mode X X
Smartcard mode X
Single-wire half-duplex communication X X
IrDA SIR ENDEC block X
LIN mode X
Dual clock domain and wakeup from Stop mode X
Receiver timeout interrupt X
Modbus communication X
Auto baud rate detection X
Driver Enable X X