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UART Modules
Freescale Semiconductor
26-9
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
26.3.4
UART Clock Select Registers (UCSRn)
The UCSRs select an external clock on the DTIN input (divided by 1 or 16) or a prescaled internal bus
clock as the clocking source for the transmitter and receiver. See
Section 26.4.1, “Transmitter/Receiver
.” The transmitter and receiver can use different clock sources. To use the internal bus clock
for both, set UCSR
n
to 0xDD.
26.3.5
UART Command Registers (UCRn)
The UCRs supply commands to the UART. Only multiple commands that do not conflict can be specified
in a single write to a UCR
n
. For example,
RESET
TRANSMITTER
and
ENABLE
TRANSMITTER
cannot be
specified in one command.
1
FFULL
FIFO full.
0 The FIFO is not full but may hold up to two unread characters.
1 A character was received and the receiver FIFO is now full. Any characters received when the FIFO is full are lost.
0
RXRDY
Receiver ready.
0 The CPU has read the receive buffer and no characters remain in the FIFO after this read.
1 One or more characters were received and are waiting in the receive buffer FIFO.
IPSBAR
Offset:
0x00_0204 (UCSR0)
0x00_0244 (UCSR1)
0x00_0284 (UCSR2)
Access: User write-only
7
6
5
4
3
2
1
0
R
W
RCS
TCS
Reset:
See Note
See Note
Note: The RCS and TCS reset values are set so the receiver and transmiter use the prescaled internal bus
clock as their clock source.
Figure 26-6. UART Clock Select Registers (UCSRn)
Table 26-6. UCSRn Field Descriptions
Field
Description
7–4
RCS
Receiver clock select. Selects the clock source for the receiver.
1101 Prescaled internal bus clock (f
sys
)
1110 DTINn divided by 16
1111 DTINn
3–0
TCS
Transmitter clock select. Selects the clock source for the transmitter.
1101 Prescaled internal bus clock (f
sys
)
1110 DTINn divided by 16
1111 DTINn
Table 26-5. USRn Field Descriptions (continued)
Field
Description
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60