MC68HC705C8A_13 Datasheet, PDF (84/222 Pages) Freescale Semiconductor, Inc – Technical Data

Freescale Semiconductor, Inc.
Parallel Input/Output (I/O)
When a port B pin is programmed as an output, reading the port bit reads
the value of the data latch and not the voltage on the pin itself. When a
port B pin is programmed as an input, reading the port bit reads the
voltage level on the pin. The data latch can always be written, regardless
of the state of its DDRB bit.
Table 7-2. Port B Pin Functions
DDRB Bit I/O Pin Mode
Accesses to DDRB
Read/Write
0
Input, Hi-Z⁽¹⁾
DDRB7–DDRB0
1
Output
DDRB7–DDRB0
1. Hi-Z = high impedance
2. Writing affects data register but does not affect input.
Accesses to PORTB
Read
Write
Pin
PB7–PB0⁽²⁾
PB7–PB0 PB7–PB0
NOTE:
To avoid excessive current draw, tie all unused input pins to V_DD or V_SS,
or for I/O pins change to outputs by writing to DDRB in user code as early
as possible.
Technical Data
84
Parallel Input/Output (I/O)
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MC68HC705C8A — Rev. 3