SWRU543B January 2019 – June 2025 CC3230S , CC3230SF , CC3235MODS , CC3235MODSF , CC3235S , CC3235SF
Hardware flow control between two devices is accomplished by connecting the U1RTS output to the clear-to-send input on the receiving device, and connecting the request-to-send output on the receiving device to the U1RTS input.
The U1RTS input controls the transmitter. The transmitter may only transmit data when the U1RTS input is asserted. The U1RTS output signal indicates the state of the RX FIFO. U1CTS remains asserted until the preprogrammed watermark level is reached, indicating that the RX FIFO has no space to store additional characters.
The UARTCTL register bits 15 (CTSEN) and 14 (RTSEN) specify the flow control mode as shown in Table 6-1.
| CTSEN | RTSEN | Description |
|---|---|---|
| 1 | 1 | RTS and CTS flow control enabled |
| 1 | 0 | Only CTS flow control enabled |
| 0 | 1 | Only RTS flow control enabled |
| 0 | 0 | RTS and CTS flow control disabled |
When RTSEN is 1, software cannot modify the U1RTS output value through the UARTCTL register request-to-send (RTS) bit, and the status of the RTS bit should be ignored.