MC68HC705K1 Datasheet, PDF (68/140 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Parallel Input/Output (I/O)
When a port A pin is programmed as an output, reading the port bit
actually reads the value of the data latch and not the voltage on the pin
itself. When a port A 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 data direction register bit. Table 7-1
summarizes the operations of the port A pins.
Table 7-1. Port A Pin Functions
Pulldown _{Control Bits}
Mask
Option _{PDIAx DDRAx}
I/O Pin
Mode
Accesses
to PDRA
Read
Write
Accesses
to DDRA
Read/Write
Accesses
to PORTA
Read
Write
No
X⁽¹⁾
0
Input, hi-z _U⁽²⁾ PDIA7–PDIA0 DDRA7–DDRA0 Pin PA7–PA0
No
X
1
Output
U PDIA7–PDIA0 DDRA7–DDRA0 PA7-PA0 PA7–PA0
Yes
0
0
Input,
pulldown on
U
PDIA7–PDIA0 DDRA7–DDRA0
Pin
PA7–PA0
Yes
0
1
Output
U PDIA7–PDIA0 DDRA7–DDRA0 PA7-PA0 PA7–PA0
Yes
1
0
Input, hi-z U PDIA7–PDIA0 DDRA7–DDRA0 Pin PA7–PA0
Yes
1
1
Output
U PDIA7–PDIA0 DDRA7–DDRA0 PA7-PA0 PA7–PA0
1. X = Don’t care
2. U = Undefined
7.5 Port B
Port B is a 2-bit, general-purpose, bidirectional I/O port with these
features:
• Programmable pulldown devices
• Oscillator output for 3-pin resistance-capacitance (RC) oscillator
configuration
7.5.1 Port B Data Register
The port B data register (PORTB) contains a bit for each of the port B
pins. When a port B pin is programmed to be an output, the state of its
data register bit determines the state of the output pin. When a port B pin
Technical Data
Parallel Input/Output (I/O)
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MC68HC705K1 — Rev. 2.0