mc68hc908mr32 Freescale Semiconductor, Inc, mc68hc908mr32 Datasheet - Page 104

• Manufacturer Part Number: mc68hc908mr32
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports (PORTS)
When bit DDRAx is a logic 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a
logic 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit.
10.3 Port B
Port B is an 8-bit, general-purpose, bidirectional I/O port that shares its pins with the analog-to-digital
convertor (ADC) module.
10.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the eight port B pins.
PTB[7:0] — Port B Data Bits
104
These read/write bits are software-programmable. Data direction of each port B pin is under the control
of the corresponding bit in data direction register B. Reset has no effect on port B data.
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
DDRA Bit
Address:
0
1
Reset:
Read:
Write:
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
READ PTA ($0000)
$0001
PTB7
Bit 7
PTA Bit
X
X
(1)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Figure 10-5. Port B Data Register (PTB)
PTB6
6
I/O Pin Mode
Table 10-1. Port A Pin Functions
Input, Hi-Z
RESET
Figure 10-4. Port A I/O Circuit
Output
PTB5
5
(2)
Table 10-1
Unaffected by reset
PTB4
DDRAx
PTAx
4
Accesses to DDRA
Read/Write
DDRA[7:0]
DDRA[7:0]
summarizes the operation of the port A pins.
PTB3
3
PTB2
2
PTA[7:0]
Read
PTB1
Pin
Accesses to PTA
1
Freescale Semiconductor
PTB0
Bit 0
PTA[7:0]
PTA[7:0]
PTAx
Write
(3)