45.7.3 USART Mode Register

This register can only be written if the WPEN bit is cleared in the USART Write Protection Mode Register.

For SPI configuration, see “USART Mode Register (SPI_MODE)”.

Name:	US_MR
Offset:	0x0004
Reset:	0x0
Property:	Read/Write


Bit	31	30	29	28	27	26	25	24
	ONEBIT	MODSYNC	MAN	FILTER		MAX_ITERATION[2:0]
Access	R/W	R/W	R/W	R/W		R/W	R/W	R/W
Reset	0	0	0	0		0	0	0


Bit	23	22	21	20	19	18	17	16
	INVDATA	VAR_SYNC	DSNACK	INACK	OVER	CLKO	MODE9	MSBF
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0


Bit	15	14	13	12	11	10	9	8
	CHMODE[1:0]		NBSTOP[1:0]		PAR[2:0]			SYNC
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0


Bit	7	6	5	4	3	2	1	0
	CHRL[1:0]		USCLKS[1:0]		USART_MODE[3:0]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0

Bit 31 – ONEBIT Start Frame Delimiter Selector

Value	Description
0	Start frame delimiter is COMMAND or DATA SYNC.
1	Start frame delimiter is one bit.

Bit 30 – MODSYNC Manchester Synchronization Mode

Value	Description
0	The Manchester start bit is a 0 to 1 transition
1	The Manchester start bit is a 1 to 0 transition.

Bit 29 – MAN Manchester Encoder/Decoder Enable

Value	Description
0	Manchester encoder/decoder are disabled.
1	Manchester encoder/decoder are enabled.

Bit 28 – FILTER Receive Line Filter

Value	Description
0	The USART does not filter the receive line.
1	The USART filters the receive line using a three-sample filter (1/16-bit clock) (2 over 3 majority).

Bits 26:24 – MAX_ITERATION[2:0] Maximum Number of Automatic Iteration

Value	Description
0–7	Defines the maximum number of iterations in ISO7816 mode, protocol T = 0.

Bit 23 – INVDATA Inverted Data

Value	Description
0	The data field transmitted on TXD line is the same as the one written in US_THR or the content read in US_RHR is the same as RXD line. Normal mode of operation.
1	The data field transmitted on TXD line is inverted (voltage polarity only) compared to the value written on US_THR or the content read in US_RHR is inverted compared to what is received on RXD line (or ISO7816 IO line). Inverted mode of operation, useful for contactless card application. To be used with configuration bit MSBF.

Bit 22 – VAR_SYNC Variable Synchronization of Command/Data Sync Start Frame Delimiter

Value	Description
0	User defined configuration of command or data sync field depending on MODSYNC value.
1	The sync field is updated when a character is written into US_THR.

Bit 21 – DSNACK Disable Successive NACK

MAX_ITERATION field must be set to 0 if DSNACK is cleared.

Value	Description
0	NACK is sent on the ISO line as soon as a parity error occurs in the received character (unless INACK is set).
1	Successive parity errors are counted up to the value specified in the MAX_ITERATION field. These parity errors generate a NACK on the ISO line. As soon as this value is reached, no additional NACK is sent on the ISO line. The flag ITER is asserted.

Bit 20 – INACK Inhibit Non Acknowledge

Value	Description
0	The NACK is generated.
1	The NACK is not generated.

Bit 19 – OVER Oversampling Mode

Value	Description
0	16X Oversampling
1	8X Oversampling

Bit 18 – CLKO Clock Output Select

Value	Description
0	The USART does not drive the SCK pin.
1	The USART drives the SCK pin if USCLKS does not select the external clock SCK.

Bit 17 – MODE9 9-bit Character Length

Value	Description
0	CHRL defines character length.
1	9-bit character length.

Bit 16 – MSBF Bit Order

Value	Description
0	Least significant bit is sent/received first.
1	Most significant bit is sent/received first.

Bits 15:14 – CHMODE[1:0] Channel Mode

Value	Name	Description
0	NORMAL	Normal mode
1	AUTOMATIC	Automatic Echo. Receiver input is connected to the TXD pin.
2	LOCAL_LOOPBACK	Local Loopback. Transmitter output is connected to the Receiver Input.
3	REMOTE_LOOPBACK	Remote Loopback. RXD pin is internally connected to the TXD pin.

Bits 13:12 – NBSTOP[1:0] Number of Stop Bits

Value	Name	Description
0	1_BIT	1 stop bit
1	1_5_BIT	1.5 stop bit (SYNC = 0) or reserved (SYNC = 1)
2	2_BIT	2 stop bits

Bits 11:9 – PAR[2:0] Parity Type

Value	Name	Description
0	EVEN	Even parity
1	ODD	Odd parity
2	SPACE	Parity forced to 0 (Space)
3	MARK	Parity forced to 1 (Mark)
4	NO	No parity
6	MULTIDROP	Multidrop mode

Bit 8 – SYNC Synchronous Mode Select

Value	Description
0	USART operates in Asynchronous mode.
1	USART operates in Synchronous mode.

Bits 7:6 – CHRL[1:0] Character Length

Value	Name	Description
0	5_BIT	Character length is 5 bits
1	6_BIT	Character length is 6 bits
2	7_BIT	Character length is 7 bits
3	8_BIT	Character length is 8 bits

Bits 5:4 – USCLKS[1:0] Clock Selection

Value	Name	Description
0	MCK	Peripheral clock is selected
1	DIV	Peripheral clock divided (DIV=DIV=8) is selected
2	PCK	PMC programmable clock (PCK) is selected. If the SCK pin is driven (CLKO = 1), the CD field must be greater than 1.
3	SCK	Serial clock (SCK) is selected

Bits 3:0 – USART_MODE[3:0] USART Mode of Operation

Value	Name	Description
0x0	NORMAL	Normal mode
0x1	RS485	RS485
0x2	HW_HANDSHAKING	Hardware Handshaking
0x3	MODEM	Modem
0x4	IS07816_T_0	IS07816 Protocol: T = 0
0x6	IS07816_T_1	IS07816 Protocol: T = 1
0x8	IRDA	IrDA
0x9	LON	LON
0xA	LIN_Host	LIN Host mode
0xB	LIN_Client	LIN Client mode
0xE	SPI_Host	SPI Host mode (CLKO must be written to 1 and USCLKS = 0, 1 or 2)
0xF	SPI_Client	SPI Client mode

The online versions of the documents are provided as a courtesy. Verify all content and data in the device’s PDF documentation found on the device product page.