EFM32WG Datasheet, PDF (501/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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When 8 data-bit frame formats are used, only the 8 least significant bits of LEUARTn_STARTFRAME
are compared to incoming frames. The full length of LEUARTn_STARTFRAME is used when operating
with frames consisting of 9 data bits.
Note
The receiver must be enabled for start frames to be detected. In addition, a start frame with
a parity error or framing error is not detected as a start frame.
19.3.5.7 Programmable Signal Frame
As well as the configurable start frame, a special signal frame can be specified. When a frame matching
the frame defined in LEUARTn_SIGFRAME is detected by the receiver, the SIGF interrupt flag in
LEUARTn_IF is set. As for start frame detection, the receiver must be enabled for signal frames to be
detected.
One use of the programmable signal frame is to signal the end of a multi-frame message transmitted to
the LEUART. An interrupt will then be triggered when the packet has been completely received, allowing
software to process it. Used in conjunction with the programmable start frame and DMA, this makes it
possible for the LEUART to automatically begin the reception of a packet on a specified start frame,
load the entire packet into memory, and give an interrupt when reception of a packet has completed.
The device can thus wait for data packets in EM2, and only be woken up when a packet has been
completely received.
A signal frame with a parity error or framing error is not detected as a signal frame.
19.3.5.8 Multi-Processor Mode
To simplify communication between multiple processors and maintain compatibility with the USART, the
LEUART supports a multi-processor mode. In this mode the 9th data bit in each frame is used to indicate
whether the content of the remaining 8 bits is data or an address.
When multi-processor mode is enabled, an incoming 9-bit frame with the 9th bit equal to the value of
MPAB in LEUARTn_CTRL is identified as an address frame. When an address frame is detected, the
MPAF interrupt flag in LEUARTn_IF is set, and the address frame is loaded into the receive register.
This happens regardless of the value of RXBLOCK in LEUARTn_STATUS.
Multi-processor mode is enabled by setting MPM in LEUARTn_CTRL. The mode can be used in buses
with multiple slaves, allowing the slaves to be addressed using the special address frames. An addressed
slave, which was previously blocking reception using RXBLOCK, would then unblock reception, receive
a message from the bus master, and then block reception again, waiting for the next message. See the
USART for a more detailed example.
Note
The programmable start frame functionality can be used for automatic address matching,
enabling reception on a correctly configured incoming frame.
An address frame with a parity error or a framing error is not detected as an address frame.
19.3.6 Loopback
The LEUART receiver samples LEUn_RX by default, and the transmitter drives LEUn_TX by default.
This is not the only configuration however. When LOOPBK in LEUARTn_CTRL is set, the receiver is
connected to the LEUn_TX pin as shown in Figure 19.5 (p. 502) . This is useful for debugging, as the
LEUART can receive the data it transmits, but it is also used to allow the LEUART to read and write to
the same pin, which is required for some half duplex communication modes. In this mode, the LEUn_TX
pin must be enabled as an output in the GPIO.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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