mc68hc11c0 Freescale Semiconductor, Inc, mc68hc11c0 Datasheet - Page 59

• Manufacturer Part Number: mc68hc11c0
• Description: 8-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

DODM — Port D Open Drain Mode
DOD[6:0] — Port D Open Drain Bits [6:0]
10.1 Serial Communications Interface (SCI)
MC68HC11C0
MC68HC11C0TS/D
RESET:
DIOCTL
Notes:
Each DODM bit controls an individual port D pin and is valid only if the pin is configured as an output.
The SCI is a universal asynchronous receiver transmitter (UART) serial communications interface, an
independent serial I/O subsystem in the MC68HC11C0. It has a standard NRZ format (one start bit,
eight or nine data bits and one stop bit) and several baud rates available. The SCI transmitter and re-
ceiver are independent, but use the same data format and bit rate. Refer to the two tables in the BAUD
register description for a summary of the SCI baud rate values.
The MC68HC11C0 SCI system supports single-wire transmit and receive operation. Although SCI sys-
tems in other M68HC11 MCUs support external wire-OR operation, two pins are necessary to perform
that function. The DIO0 bit in DIOCTL register controls the SCI mode of operation. When single-wire
operation is selected (DIO0 = 1), the SCI uses only PD1 for its transmit and receive signals. In this
mode, if the receiver is enabled, PD1 is the RxD input; if the transmitter is enabled, PD1 is the TxD out-
put. If both the receiver and the transmitter are enabled, both RxD and TxD are internally tied together
Bit 0
0
1
1. If a pin is configured for general-purpose I/O, the DDRD bit controls the direction of data.
2. If a pin is configured for RxD input, there is no weak pull-up at the pin.
3. If a pin is configured for TxD output, the output can be either an open-drain output or a CMOS driver. This is
4. TE is the transmitter enable bit. RE is the receiver enable bit. Refer to the SCCR2 register.
controlled by the port D driver output mode (DODM) register.
0 = Corresponding port D output pin configured as normal CMOS driver.
1 = Corresponding port D output pin configured as open-drain output driver.
Bit 7
—
0
SCI Enables
If any of the pins PD[5:2] are configured as SPI inputs they will not have pull-ups.
If any of the pins PD[5:2] are configured as SPI outputs they will be either open-
drain outputs or normal CMOS driver outputs depending on the state of the corre-
sponding bit in the DODM register.
RE = 0
RE = 0
RE = 0
RE = 0
TE = 1
TE = 0
TE = 1
TE = 1
TE = 1
TE = 1
DOD6
6
0
Freescale Semiconductor, Inc.
RxD/TxD
Looped
For More Information On This Product,
DOD5
PD1
TxD
TxD
RxD
I/O
I/O
5
0
Table 15 PD[1:0] Configuration
Go to: www.freescale.com
DOD4
4
0
Control
Pull-Up
DDD1
DDD1
Off
Off
Off
Off
NOTE
DOD3
3
0
SCI Enables
RE = 1
RE = 0
X
DOD2
2
0
DOD1
PD0
RxD
1
0
I/O
I/O
DOD0
Bit 0
$0075
0
Control
Pull-Up
DDD0
DDD0
Off
MOTOROLA
Single Wire
Two Wire
Mode
SCI
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