MMC2001
UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER MODULE
MOTOROLA
REFERENCE MANUAL
11-9
*n = 0, 1, . . ., 15
X = Undefined
Figure 11-3 UART Transmitter Register
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.
11.4.3 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.
Figure 11-4 UART Control Register 1
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:
At reset, these bits are cleared to zero.
U0TX — UART0 Transmitter Register
10009040
U1TX — UART1 Transmitter Register
1000A040
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
TX DATA
RESET:
0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
U0CR1 — UART0 Control Register 1
10009080
U1CR1 — UART1 Control Register 1
1000A080
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
TxFL
TRDY-
EN
TXEN
RxFL
RRDY
EN
RXEN
IREN
0
RTSD
EN
SND-
BRK
0
0
DOZE
UART
EN
W
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
Table 11-2 TxFL Field Settings
Value
Meaning
00
Interrupt if TX FIFO has a slot for one or more character
01
Interrupt if TX FIFO has a slot for four or more characters
10
Interrupt if TX FIFO has a slot for eight or more characters
11
Interrupt if TX FIFO has a slot for fourteen or more characters
Freescale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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