
Register Description and Programming
MOTOROLA
UART Modules
15-21
15.4.1.6.1
Reset Mode Register Pointer
The reset mode register pointer command causes the mode register pointer to point to UMR1.
15.4.1.6.2
Reset Receiver
The reset receiver command resets the receiver. The receiver is immediately disabled, the FFULL and
RxRDY bits in the USR are cleared, and the receiver FIFO pointer is reinitialized. All other registers are
unaltered. Use this command instead of the receiver-disable command whenever the receiver
configuration is changed (it places the receiver in a known state).
15.4.1.6.3
Reset Transmitter
The reset transmitter command resets the transmitter. The transmitter is immediately disabled and the
TxEMP and TxRDY bits in the USR are cleared. All other registers are unaltered. Use this command
instead of the transmitter-disable command whenever the transmitter configuration is changed (it places
the transmitter in a known state).
15.4.1.6.4
Reset Error Status
The reset error status command clears the RB, FE, PE, and OE bits in the USR. This command is also
used in the block mode to clear all error bits after a data block is received.
15.4.1.6.5
Reset Break-Change Interrupt
The reset break-change interrupt command clears the delta break (DBx) bit in the UISR.
15.4.1.6.6
Start Break
The start break command forces TxD low. If the transmitter is empty, the start of the break conditions can
be delayed by as much as two bit times. If the transmitter is active, the break begins when transmission of
the character is complete. If a character is in the transmitter shift register, the start of the break is delayed
until the character is transmitted. If the transmitter holding register has a character, that character is
transmitted before the break. The transmitter must be enabled for this command to be accepted. The state
of the CTS input is ignored for this command.
15.4.1.6.7
Stop Break
The stop break command causes TxD to go high (mark) within two bit times. Characters stored in the
transmitter buffer, if any, are transmitted.
15.4.1.7
Transmitter Commands
Bits TC1 and TC0 select a single command as listed in
Table 15-14.
MISC2
MISC1
MISC0
COMMAND
1
0
Reset Error Status
1
0
1
Reset Break-Change Interrupt
1
0
Start Break
1
Stop Break
Table 15-13 MISCx Control Bits (Continued)
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