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UART Modules
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
16-10
Freescale Semiconductor
16.3.6
UART Receiver Buffers (URB
n
)
The receiver buffers contain one serial shift register and a 24-byte FIFO. RxD is connected to the serial
shift register. The CPU reads from the top of the stack while the receiver shifts and updates from the
bottom when the shift register is full (see
). RB contains the character in the receiver.
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. USR
n
[TxEMP,TxRDY] are set. If the
transmitter is already enabled, this command has no effect.
10
transmitter disable
Terminates transmitter operation and clears USR
n
[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.
1–0
RC
(This field selects a single command)
00
no action taken
Causes the receiver to stay in its current mode. If the receiver is enabled, it remains
enabled; if disabled, it remains disabled.
01
receiver enable
If the UART module is not in multidrop mode (UMR1
n
[PM] ¦ 11),
RECEIVER
ENABLE
enables the channel's receiver and forces it into search-for-start-bit state. If the receiver
is already enabled, this command has no effect.
10
receiver disable
Disables the receiver immediately. Any character being received is lost. The command
does not affect receiver status bits or other control registers. If the UART module is
programmed for local loop-back or multidrop mode, the receiver operates even though
this command is selected. If the receiver is already disabled, the command has no
effect.
11
—
Reserved, do not use.
7
0
Field
RB
Reset
0000_0000
R/W
Read only
Address
MBAR + 0x10C,0x14C
Figure 16-7. UART Receiver Buffer (URB
n
)
Table 16-6. UCR
n
Field Descriptions (continued)
Bits
Value
Command
Description