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TX DATA — Transmit Data
These write-only bits are the parallel transmit data inputs. In 7-bit mode, D7 is
ignored. In 8-bit mode, all bits are used. Data is transmitted LSB first. A new charac-
ter is transmitted when these bits are written. These bits must be written only while
TRDY is high to ensure that corrupted data is not sent.
C.9.3 UART Control Register 1 (UCR1)
UART control register 1 is a read/write register. This register enables the UART and
the transmit and receive blocks. It controls the Tx and Rx FIFO levels and enables the
TRDY and RRDY interrupts.
U0CR1 — UART0 Control Register 1
U1CR1 — UART1 Control Register 1
15
14
13
12
R
TRDY-
TxFL
TXEN
EN
W
RESET:
0
0
0
0
TxFL — Transmitter FIFO Interrupt Trigger Level
These bits control the operation of the interrupt generated by the transmitter. A
maskable interrupt is generated whenever the data level in the TX FIFO drops below
the selected threshold. The bits are encoded as follows:
Value
00
01
10
11
At reset, these bits are cleared to zero.
TRDYEN — Transmitter Ready Interrupt Enable
Setting this bit enables an interrupt when the transmitter has one or more slots avail-
able in the TX FIFO. The fill level in the TX FIFO at which an interrupt is generated is
controlled by the TxFL bits. While this bit is negated, the transmitter interrupt is dis-
abled.
0 = TX interrupt disabled
1 = TX interrupt enabled
At reset, this bit is cleared to zero.
TXEN — Transmitter Enable
This bit enables or disables the transmitter. While UARTEN and TXEN bits are set,
and DOZE bit is cleared, the transmitter is enabled. If this bit is cleared in the middle
of a transmission, the UART disables the transmitter immediately and starts marking
ones.
MOTOROLA
C-38
All manuals and user guides at all-guides.com
Freescale Semiconductor, Inc.
11
10
9
8
RRDY
RxFL
RXEN IREN
EN
0
0
0
0
Figure C-38 UART Control Register 1
Table C-18 TxFL Field Settings
Interrupt if TX FIFO has a slot for one or more character
Interrupt if TX FIFO has a slot for four or more characters
Interrupt if TX FIFO has a slot for eight or more characters
Interrupt if TX FIFO has a slot for fourteen or more characters
PROGRAMMING REFERENCE
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Go to: www.freescale.com
7
6
5
4
0
RTSD
SND-
EN
BRK
0
0
0
Meaning
10009080
1000A080
3
2
1
0
0
0
UART
DOZE
EN
0
0
MMC2001
REFERENCE MANUAL
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