MC68HC05K0 Datasheet, PDF (67/154 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Parallel Input/Output (I/O)
Port A
7.3.2 Data Direction Register A
The contents of data direction register A (DDRA), shown in Figure 7-2,
determine whether each port A pin is an input or an output. Writing a
logic 1 to a DDRA bit enables the output buffer for the associated port A
pin; a logic 0 disables the output buffer. A reset initializes all DDRA bits
to logic 0s, configuring all port A pins as inputs. If the pulldown devices
are enabled by mask option, setting a DDRA bit to a logic 1 turns off the
pulldown device for that pin.
Address: $0004
Bit 7
6
5
4
3
2
1
Read:
DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1
Write:
Reset: 0
0
0
0
0
0
0
Figure 7-2. Data Direction Register A (DDRA)
Bit 0
DDRA0
0
DDRA7–DDRA0 — Port A Data Direction Bits
These read/write bits control port A data direction. Reset clears bits
DDRA7–DDRA0.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE: Avoid glitches on port A pins by writing to the port A data register before
changing DDRA bits from logic 0 to logic 1.
MC68HC05K0 • MC68HC05K1 — Rev. 2.0
Parallel Input/Output (I/O)
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Technical Data