Usart Request Register (Usart_Rqr) - ST STM32G0 1 Series Reference Manual

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Universal synchonous receiver transmitter (USART)

Bits 31:24 BLEN[7:0]: Block Length

This bitfield gives the Block length in Smartcard T = 1 Reception. Its value equals the

number of information characters + the length of the Epilogue Field (1-LEC/2-CRC) - 1.

BLEN = 0: 0 information characters + LEC

BLEN = 1: 0 information characters + CRC

BLEN = 255: 254 information characters + CRC (total 256 characters))

In Smartcard mode, the Block length counter is reset when TXE = 0 (TXFE = 0 in case FIFO

mode is enabled).

This bitfield can be used also in other modes. In this case, the Block length counter is reset

when RE = 0 (receiver disabled) and/or when the EOBCF bit is written to 1.

Note: This value can be programmed after the start of the block reception (using the data

Bits 23:0 RTO[23:0]: Receiver timeout value

This bitfield gives the Receiver timeout value in terms of number of bits during which there is

no activity on the RX line.

In standard mode, the RTOF flag is set if, after the last received character, no new start bit is

detected for more than the RTO value.

In Smartcard mode, this value is used to implement the CWT and BWT. See Smartcard

chapter for more details. In the standard, the CWT/BWT measurement is done starting from

the start bit of the last received character.

Note: This value must only be programmed once per received character.

RTOR can be written on-the-fly. If the new value is lower than or equal to the counter, the

RTOF flag is set.

This register is reserved and forced by hardware to "0x00000000" when the Receiver

timeout feature is not supported. Refer to