UART ModulesMCF5253 Reference Manual, Rev. 115-22 Freescale Semiconductor15.4.5.2.2 Transmitter EnableThe “transmitter enable” command enables operation of the channel's transmitter. The TxEMP andTxRDY bits in the USR are also set. If the transmitter is already enabled, this command has no effect.15.4.5.2.3 Transmitter DisableThe “transmitter disable” command terminates transmitter operation and clears the TxEMP and TxRDYbits in the USR. However, if a character is being transmitted when the transmitter is disabled, thetransmission of the character is completed before the transmitter becomes inactive. If the transmitter isalready disabled, this command has no effect.15.4.5.2.4 Do Not UseDo not use this bit combination because the result is indeterminate.15.4.5.3 Receiver CommandsBits RC1 and RC0 select a single command as listed in Table 15-11.15.4.5.3.1 No Action TakenThe “no action taken” command causes the receiver to stay in its current mode. If the receiver is enabled,it remains enabled; if disabled, it remains disabled.15.4.5.3.2 Receiver EnableThe “receiver enable” command enables operation of the channel's receiver. If the UART module is not inmultidrop mode, this command also forces the receiver into the search-for-start-bit state. If the receiver isalready enabled, this command has no effect.15.4.5.3.3 Receiver DisableThe “receiver disable” command immediately disables the receiver. Any character being received is lost.The command has no effect on the receiver status bits or any other control register. If the UART moduleis programmed to operate in the local loopback mode or multidrop mode, the receiver operates even thoughthis command is selected. If the receiver is already disabled, this command has no effect.15.4.5.3.4 Do Not UseDo not use this bit combination because the result is indeterminate.Table 15-11. RCx Control BitsRC1 RC0 Command0 0 No Action Taken0 1 Receiver Enable1 0 Receiver Disable1 1 Do Not Use
