MOTOROLA
UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER MODULE
MMC2001
11-16
REFERENCE MANUAL
11.5 GPIO Pins and Registers
The GPIO functionality of UART pins is controlled by three registers: the port control
register (UPCR), data direction register (UDDR), and port data register (UPDR).
11.5.1 UART Port Control Register (UPCR)
The read/write UART port control register controls the functionality of UART GPIO
pins.
Figure 11-9 UART Port Control Register
PCx — Port Control Bit x
0 =
Corresponding pin is configured as GPIO pin
1 =
Corresponding pin is configured as UART pin
At reset, these bits are cleared to zero.
11.5.2 UART Data Direction Register (UDDR)
The read/write UART data direction register controls the direction of UART GPIO
pins.
Figure 11-10 UART Data Direction Register
Table 11-4 UART Pins GPIO Assignment
GPIO Bit
UART Pin
P0
RXD
P1
TXD
P2
RTS
P3
CTS
U0PCR — UART0 Port Control Register
1000908A
U1PCR — UART1 Port Control Register
1000A08A
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
0
0
0
0
PC3
PC2
PC1
PC0
W
RESET:
0
0
0
0
U0DDR — UART0 Data Direction Register
1000908C
U1DDR — UART1 Data Direction Register
1000A08C
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
0
0
0
0
PDC3
PDC2
PDC1
PDC0
W
RESET:
0
0
0
0
Freescale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc.
..