Input/Output (I/O) Ports (PORTS)
Port F
NOTE:
Avoid glitches on port F pins by writing to the port F data register before changing
data direction register F bits from 0 to 1.
Figure 10-18 shows the port F I/O logic.
READ DDRF ($000D)
WRITE DDRF ($000D)
DDRFx
RESET
WRITE PTF ($0009)
PTFx
PTFx
READ PTF ($0009)
Figure 10-18. Port F I/O Circuit
When bit DDRFx is a logic 1, reading address $0009 reads the PTFx data latch.
When bit DDRFx is a logic 0, reading address $0009 reads the voltage level on the
pin. The data latch can always be written, regardless of the state of its data
direction bit. Table 10-6 summarizes the operation of the port F pins.
Table 10-6. Port F Pin Functions
Accesses
Accesses to PTF
DDRF
Bit
PTF
Bit
to DDRF
Read/Write
DDRF[6:0]
DDRF[6:0]
I/O Pin Mode
Read
Pin
Write
X(1)
X
Input, Hi-Z(2)
Output
PTF[6:0](3)
PTF[6:0]
0
1
PTF[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 — Rev. 6.0
MOTOROLA Input/Output (I/O) Ports (PORTS)
Data Sheet
123
FREESCALE [ Freescale ]
