Datasheet

14-14 MCF5407 User’s Manual
Register Descriptions
Table 14-11 describes UCRn fields and commands. Examples in Section 14.5.2,
“Transmitter and Receiver Operating Modes,” show how these commands are used.
76 43210
Field — MISC TC RC
Reset 0000_0000
R/W Write only
Address MBAR + 0x1C8, 0x208
Figure 14-11. UART Command Register (UCRn)
Table 14-11. UCRn Field Descriptions
Bits Value Command Description
7 ——Reserved, should be cleared.
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
In UART mode, immediately 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. When UART1 is in modem mode, TxEMP is
not cleared by this soft reset. It is cleared the same way as the Rx overflow bit,
by a
RESET ERROR STATUS command.
100
RESET ERROR
STATUS
In UART mode, clears USRn[RB,FE,PE,OE]. Also used in block mode to clear all
error bits after a data block is received. When UART1 is in modem mode, this
command also clears TxEMP.
101
RESET BREAK–
CHANGE INTERRUPT
Clears the delta break bit, UISRn[DB]. This command has no effect in modem
mode.
110
START BREAK Forces TxD 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
and has no effect in modem mode.
111
STOP BREAK Causes TxD to go high (mark) within two bit times. Any characters in the
transmitter buffer are sent.