In transmission, the Host CPU software must exercise an element of real-time control to transmit data packets, each of which must be emitted at a constant delay from the start-bits of each individual packet. Thus, when sending a series of packets, the packet-to-packet delay must respect a specific delay. Two methods can be used to control this delay:
- Filling the TX FIFO with a number of zero bits that are transmitted with a t period
- Using an external system timer to control the delay between each start-of-frame or between the end of a frame and the start of the next one. This can be performed by:
- Controlling the start of the frame using the
UART_MDR1[5] SCT bit and the UART_ACREG[2] SCTX_EN bit, depending on the
timer status
- Using the UART_IIR_UART[5] TX_STATUS_IT interrupt
bit to preload the next frame in the TX FIFO and to control the start of
the timer (in case of control delay between the end of a frame and the
start of the next frame)