MC9S12Q FREESCALE [Freescale Semiconductor, Inc], MC9S12Q Datasheet - Page 137

• Manufacturer Part Number: MC9S12Q
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

4.3.2.4
Read: Anytime when register is in the map
Write: Anytime when register is in the map
This register controls the data direction for port B. When port B is operating as a general-purpose I/O port,
DDRB determines the primary direction for each port B pin. A 1 causes the associated port pin to be an
output and a 0 causes the associated pin to be a high-impedance input. The value in a DDR bit also affects
the source of data for reads of the corresponding PORTB register. If the DDR bit is 0 (input) the buffered
pin input state is read. If the DDR bit is 1 (output) the associated port data register bit state is read.
This register is not in the on-chip memory map in expanded and special peripheral modes. Therefore, these
accesses will be echoed externally. It is reset to 0x00 so the DDR does not override the three-state control
signals.
Freescale Semiconductor
Module Base + 0x0003
Starting address location affected by INITRG register setting.
Reset
DDRB
Field
7:0
W
R
Bit 7
Data Direction Port B
0 Configure the corresponding I/O pin as an input
1 Configure the corresponding I/O pin as an output
Data Direction Register B (DDRB)
0
7
6
0
6
Figure 4-5. Data Direction Register B (DDRB)
Table 4-4. DDRB Field Descriptions
5
0
5
MC9S12Q128
Rev 1.09
4
0
4
Description
Chapter 4 Multiplexed External Bus Interface (MEBIV3)
3
0
3
2
0
2
1
0
1
Bit 0
0
0
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