34.9.2 Control B
| Symbol | Description | Symbol | Description | Symbol | Description |
|---|---|---|---|---|---|
| R | Readable bit | HC | Cleared by Hardware | (Grey cell) | Unimplemented |
| W | Writable bit | HS | Set by Hardware | X | Bit is unknown at Reset |
| K | Write to clear | S | Software settable bit | — | — |
| Name: | CTRLB |
| Offset: | 0x04 |
| Reset: | 0x00000000 |
| Property: | RW |
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| LINCMD[1:0] | |||||||||
| Access | R/W | R/W | |||||||
| Reset | 0 | 0 | |||||||
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| FIFOCLR[1:0] | RXEN | TXEN | |||||||
| Access | RW | RW | RW | RW | |||||
| Reset | 0 | 0 | 0 | 0 | |||||
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| PMODE | ENC | SFDE | COLDEN | ||||||
| Access | RW | RW | RW | RW | |||||
| Reset | 0 | 0 | 0 | 0 |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| SBMODE | CHSIZE[2:0] | ||||||||
| Access | RW | RW | RW | RW | |||||
| Reset | 0 | 0 | 0 | 0 | |||||
Bits 25:24 – LINCMD[1:0] LIN Command
These bits define the LIN header transmission control. This field is only valid in LIN host mode (CTRLA.FORM= LIN Host).
These are strobe bits and will always read back as zero.
These bits are not enable-protected.
| Value | Name | Description |
|---|---|---|
| 0x0 | NONE | Normal USART transmission |
| 0x1 | SOFTWARE_CONTROL_TRANSMIT_CMD | Break field is transmitted when DATA is written |
| 0x2 | AUTO_TRANSMIT_CMD | Break, synch and identifier are automaticcaly transmitted when DATA is written with the identifier |
Bits 23:22 – FIFOCLR[1:0] FIFO Clear
When these bits are set, the corresponding FIFO will be cleared. The bits will automatically clear when SYNCBUSY.CTRLB = 0.
These bits are not enable-protected.
| FIFOCLR[1:0] | Name | Description |
|---|---|---|
| 0x0 | NONE | No action |
| 0x1 | TXFIFO | Clear TX FIFO |
| 0x2 | RXFIFO | Clear RX FIFO |
| 0x3 | BOTH | Clear both TX/RX FIFO |
| Value | Name | Description |
|---|---|---|
| 0x0 | NONE | No action |
| 0x1 | TXFIFO | Clear TX FIFO |
| 0x2 | RXFIFO | Clear RX FIFO |
| 0x3 | BOTH | Clear both TX and RF FIFOs |
Bit 17 – RXEN Receiver Enable
Writing '0' to this bit will disable the USART receiver. Disabling the receiver will flush the receive buffer and clear the FERR, PERR and BUFOVF bits in the STATUS register.
Writing '1' to CTRLB.RXEN when the USART is disabled will set CTRLB.RXEN immediately. When the USART is enabled, CTRLB.RXEN will be cleared, and SYNCBUSY.CTRLB will be set and remain set until the receiver is enabled. When the receiver is enabled, CTRLB.RXEN will read back as '1'.
Writing '1' to CTRLB.RXEN when the USART is enabled will set SYNCBUSY.CTRLB, which will remain set until the receiver is enabled, and CTRLB.RXEN will read back as '1'.
This bit is not enable-protected.
| Value | Description |
|---|---|
| 0 | The receiver is disabled or being enabled. |
| 1 | The receiver is enabled or will be enabled when the USART is enabled. |
Bit 16 – TXEN Transmitter Enable
Writing '0' to this bit will disable the USART transmitter. Disabling the transmitter will not become effective until ongoing and pending transmissions are completed.
Writing '1' to CTRLB.TXEN when the USART is disabled will set CTRLB.TXEN immediately. When the USART is enabled, CTRLB.TXEN will be cleared, and SYNCBUSY.CTRLB will be set and remain set until the transmitter is enabled. When the transmitter is enabled, CTRLB.TXEN will read back as '1'.
Writing '1' to CTRLB.TXEN when the USART is enabled will set SYNCBUSY.CTRLB, which will remain set until the transmitter is enabled, and CTRLB.TXEN will read back as '1'.
This bit is not enable-protected.
| Value | Description |
|---|---|
| 0 | The transmitter is disabled or being enabled. |
| 1 | The transmitter is enabled or will be enabled when the USART is enabled. |
Bit 13 – PMODE Parity Mode
This bit selects the type of parity used when parity is enabled (CTRLA.FORM is '1'). The transmitter will automatically generate and send the parity of the transmitted data bits within each frame. The receiver will generate a parity value for the incoming data and parity bit, compare it to the parity mode and, if a mismatch is detected, STATUS.PERR will be set.
This bit is not synchronized.
| Value | Name | Description |
|---|---|---|
| 0x0 | EVEN | Even parity |
| 0x1 | ODD | Odd parity |
Bit 10 – ENC Encoding Format
This bit selects the data encoding format.
This bit is not synchronized.
| Value | Name | Description |
|---|---|---|
| 0x0 | DISABLE | Data is not encoded |
| 0x1 | IRDA | Data is IrDA encoded |
Bit 9 – SFDE Start of Frame Detection Enable
This bit controls whether the start-of-frame detector will wake up the device when a start bit is detected on the RxD line.
This bit is not synchronized.
| SFDE | INTENSET.RXS | INTENSET.RXC | Description |
|---|---|---|---|
| 0 | X | X | Start-of-frame detection disabled. |
| 1 | 0 | 0 | Reserved |
| 1 | 0 | 1 | Start-of-frame detection enabled. RXC wakes up the device from all sleep modes. |
| 1 | 1 | 0 | Start-of-frame detection enabled. RXS wakes up the device from all sleep modes. |
| 1 | 1 | 1 | Start-of-frame detection enabled. Both RXC and RXS wake up the device from all sleep modes. |
Bit 8 – COLDEN Collision Detection Enable
This bit enables collision detection.
This bit is not synchronized.
| Value | Description |
|---|---|
| 0 | Collision detection is not enabled. |
| 1 | Collision detection is enabled. |
Bit 6 – SBMODE Stop Bit Mode
This bit selects the number of stop bits transmitted.
This bit is not synchronized.
| Value | Name | Description |
|---|---|---|
| 0x0 | ONE | One stop bit |
| 0x1 | TWO | Two stop bits |
Bits 2:0 – CHSIZE[2:0] Character Size
These bits select the number of bits in a character.
These bits are not synchronized.
| CHSIZE[2:0] | Description |
|---|---|
| 0x0 | 8 bits |
| 0x1 | 9 bits |
| 0x2-0x4 | Reserved |
| 0x5 | 5 bits |
| 0x6 | 6 bits |
| 0x7 | 7 bits |
| Value | Name | Description |
|---|---|---|
| 0x0 | 8BITS | 8-bits character |
| 0x1 | 9BITS | 9-bits character |
| 0x5 | 5BITS | 5-bits character |
| 0x6 | 6BITS | 6-bits character |
| 0x7 | 7BITS | 7-bits character |