mc68hc908sr12 Freescale Semiconductor, Inc, mc68hc908sr12 Datasheet - Page 322

• Manufacturer Part Number: mc68hc908sr12
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports
Data Sheet
322
NOTE:
Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
the port A I/O logic.
When DDRAx is a logic 1, reading address $0000 reads the PTAx data
latch. When 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.
Table 18-2
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
DDRA
Bit
0
1
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
READ PTA ($0000)
PTA Bit
X
summarizes the operation of the port A pins.
X
(1)
Input/Output (I/O) Ports
Table 18-2. Port A Pin Functions
Input, Hi-Z
I/O Pin Mode
Figure 18-4. Port A I/O Circuit
RESET
Output
(2)
MC68HC908SR12•MC68HC08SR12 — Rev. 5.0
Accesses to DDRA
DDRAx
PTAx
DDRA[7:0]
DDRA[7:0]
Read/Write
Freescale Semiconductor
PTA[7:0]
Figure 18-4
Read
Pin
Accesses to PTA
PTA[7:0]
PTA[7:0]
shows
Write
PTAx
(3)