MC68HC908GR8 Datasheet, PDF (154/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Input/Output Ports (I/O)
Figure 16-15 shows the port D I/O logic.
READ DDRD ($0007)
WRITE DDRD ($0007)
RESET
WRITE PTD ($0003)
DDRDx
PTDx
PTDPUEx
V_DD
INTERNAL
PULLUP
DEVICE
PTDx
READ PTD ($0003)
Figure 16-15. Port D I/O Circuit
When bit DDRDx is a 1, reading address $0003 reads the PTDx data latch. When bit DDRDx is a 0,
reading address $0003 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 16-5 summarizes the operation of the port D pins.
Table 16-5. Port D Pin Functions
PTDPUE Bit DDRD Bit PTD Bit I/O Pin Mode
1
0
X⁽¹⁾
Input, V_DD(4)
0
0
X
Input, Hi-Z⁽²⁾
X
1
X
Output
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
4. I/O pin pulled up to V_DD by internal pullup device.
Accesses to DDRD
Read/Write
DDRD6–DDRD0
DDRD6–DDRD0
DDRD6–DDRD0
Accesses to PTD
Read
Write
Pin
PTD6–PTD0⁽³⁾
Pin
PTD6–PTD0⁽³⁾
PTD6–PTD0
PTD6–PTD0
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
154
Freescale Semiconductor