Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
310 Input/Output (I/O) Ports MOTOROLA
Input/Output (I/O) Ports
15.3 Port A
Port A is an 8-bit, general-purpose, bidirectional I/O port.
15.3.1 Port A Data Register
The port A data register (PTA) contains a data latch fo r each of the eigh t
port A pins.
PTA[7:0] — Port A Data Bits
These read/write bits are software programmable. Data direction of
each port A pin is under the control of the corresponding bit in data
direction register A. Reset has no effect on port A data.
15.3.2 Data Direction Register A
Data direction register A (DDRA) determines whethe r each po rt A pin is
an input or an output. Writing a logic 1 to a D DRA bit enable s the out put
buffer for the corresponding port A pin; a logic 0 disables the output
buffer.
Address: $0000
Bit 7654321Bit 0
Read: PTA7 PTA6 PTA5 PTA4 PTA3 PTA2 PTA1 PTA0
Write:
Reset: Unaffected by reset
Figure 15-2. Port A Data Register (PTA)
Address: $0004
Bit 7654321Bit 0
Read: DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1 DDRA0
Write:
Reset:00000000
Figure 15-3. Data Direction Register A (DDRA)