Freescale Semiconductor MC68HC908MR32 - Manual (Page 110)

Input/Output (I/O) Ports (PORTS)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
110 Freescale Semiconductor
10.7 Port F
Port F is a 6-bit, special function port that shares four of its pins with the serial peripheral interface module
(SPI) and two pins with the serial communications interface (SCI).
10.7.1 Port F Data Register
The port F data register (PTF) contains a data latch for each of the six port F pins.
PTF[5:0] — Port F Data Bits
These read/write bits are software programmable. Data direction of each port F pin is under the control
of the corresponding bit in data direction register F. Reset has no effect on PTF[5:0].
NOTE
Data direction register F (DDRF) does not affect the data direction of port F
pins that are being used by the SPI or SCI module. However, the DDRF bits
always determine whether reading port F returns the states of the latches
or the states of the pins.
10.7.2 Data Direction Register F
Data direction register F (DDRF) determines whether each port F pin is an input or an output. Writing a
logic 1 to a DDRF bit enables the output buffer for the corresponding port F pin; a logic 0 disables the
output buffer.
DDRF[5:0] — Data Direction Register F Bits
These read/write bits control port F data direction. Reset clears DDRF[5:0], configuring all port F pins
as inputs.
1 = Corresponding port F pin configured as output
0 = Corresponding port F pin configured as input
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.
Address: $0009
Bit 7 6 5 4 3 2 1 Bit 0
Read: 0 0
PTF5 PTF4 PTF3 PTF2 PTF1 PTF0
Write: R R
Reset: Unaffected by reset
R = Reserved
Figure 10-16. Port F Data Register (PTF)
Address: $000D
Bit 7 6 5 4 3 2 1 Bit 0
Read: 0 0
DDRF5 DDRF4 DDRF3 DDRF2 DDRF1 DDRF0
Write: R R
Read: 0 0 0 0 0 0
R = Reserved
Figure 10-17. Data Direction Register F (DDRF)