timeout_enable=disable, tx_req_enable=disable, rx_req_enable=disable
UART DMA Request Enable Register
| rx_req_enable | DMA RX REQ Enable 0 (disable): undefined 1 (enable): undefined |
| tx_req_enable | DMA TX REQ Enable 0 (disable): undefined 1 (enable): undefined |
| timeout_enable | DMA Timeout Enable 0 (disable): undefined 1 (enable): undefined |