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Serial Module
8-24
MC68307 USER’S MANUAL
MOTOROLA
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 after the
break. The transmitter must be enabled for this command to be accepted. The state of the
CTS input is ignored for this command.
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.
TC1–TC0—Transmitter Commands
These bits select a single command as listed in
Table 8-9.No Action Taken—The no action taken command causes the transmitter to stay in its cur-
rent mode. If the transmitter is enabled, it remains enabled; if disabled, it remains dis-
abled.
Transmitter Enable—The transmitter enable command enables operation of the channel's
transmitter. The TxEMP and TxRDY bits in the USR are also set. If the transmitter is al-
ready enabled, this command has no effect.
Transmitter Disable—The transmitter disable command terminates transmitter operation
and clears the TxEMP and TxRDY bits in the USR. However, if a character is being trans-
mitted when the transmitter is disabled, the transmission of the character is completed be-
fore the transmitter becomes inactive. If the transmitter is already disabled, this command
has no effect.
Do Not Use—Do not use this bit combination because the result is indeterminate.
RC1–RC0—Receiver Commands
These bits select a single command as listed in
Table 8-10.No Action Taken—The 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.
Receiver Enable—The receiver enable command enables operation of the channel's re-
ceiver. If the serial module is not in multidrop mode, this command also forces the receiver
Table 8-9. TCx Control Bits
TC1
TC0
Command
0
No Action Taken
0
1
Enable Transmitter
1
0
Disable Transmitter
1
Do Not Use
Table 8-10. RCx Control Bits
RC1
RC0
Command
0
No Action Taken
0
1
Enable Receiver
1
0
Disable Receiver
1
Do Not Use