Microcontroller User's Manual

23-10 MCF5282 User’s Manual MOTOROLA
Register Descriptions
Table 23-6. UCRn Field Descriptions
Bits Value Command Description
6–4
MISC Field (This field selects a single command.)
000
NO COMMAND —
001 RESET MODE
REGISTER POINTER
Causes the mode register pointer to point to UMR1n.
010 RESET RECEIVER Immediately disables the receiver, clears USRn[FFULL,RxRDY], and reinitializes the
receiver FIFO pointer. No other registers are altered. Because it places the receiver in a
known state, use this command instead of
RECEIVER DISABLE when reconfiguring the
receiver.
011 RESET TRANSMITTER Disables the transmitter and clears USRn[TxEMP,TxRDY]. No other registers are altered.
Because it places the transmitter in a known state, use this command instead of
TRANSMITTER DISABLE when reconfiguring the transmitter.
100 RESET ERROR STATUS Clears USRn[RB,FE,PE,OE]. Also used in block mode to clear all error bits after a data
block is received.
101 RESET BREAK–
CHANGE INTERRUPT
Clears the delta break bit, UISRn[DB].
110
START BREAK Forces UTXD low. If the transmitter is empty, the break may be delayed up to one bit time.
If the transmitter is active, the break starts when character transmission completes. The
break is delayed until any character in the transmitter shift register is sent. Any character
in the transmitter holding register is sent after the break. The transmitter must be enabled
for the command to be accepted. This command ignores the state of CTS
.
111 STOP BREAK Causes UTXD to go high (mark) within two bit times. Any characters in the transmit buffer
are sent.
3–2
TC Field (This field selects a single command)
00
NO ACTION TAKEN Causes the transmitter to stay in its current mode: if the transmitter is enabled, it remains
enabled; if the transmitter is disabled, it remains disabled.
01 TRANSMITTER
ENABLE
Enables operation of the channel’s transmitter. USRn[TxEMP,TxRDY] are set. If the
transmitter is already enabled, this command has no effect.
10
TRANSMITTER
DISABLE
Terminates transmitter operation and clears USRn[TxEMP,TxRDY]. If a character is being
sent when the transmitter is disabled, transmission completes before the transmitter
becomes inactive. If the transmitter is already disabled, the command has no effect.
11 — Reserved, do not use.