MC68908GZ8MFJE Datasheet, PDF (163/314 Pages) Freescale Semiconductor, Inc – Microcontrollers

Port C
DDRC6–DDRC0 — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears DDRC6–DDRC0, configuring all port
C pins as inputs.
1 = Corresponding port C pin configured as output
0 = Corresponding port C pin configured as input
NOTE
Avoid glitches on port C pins by writing to the port C data register before
changing data direction register C bits from 0 to 1.
Figure 13-11 shows the port C I/O logic.
READ DDRC ($0006)
WRITE DDRC ($0006)
RESET
WRITE PTC ($0002)
V_DD
DDRCx
PTCx
PTCPUEx
READ PTC ($0002)
INTERNAL
PULLUP
DEVICE
PTCx
Figure 13-11. Port C I/O Circuit
When bit DDRCx is a logic 1, reading address $0002 reads the PTCx data latch. When bit DDRCx is a
logic 0, reading address $0002 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 13-4 summarizes the operation of the port C pins.
Table 13-4. Port C Pin Functions
PTCPUE
Bit
DDRC
Bit
PTC
Bit
I/O Pin
Mode
Accesses to DDRC
Read/Write
1
0
X⁽¹⁾
Input, V_DD(2)
DDRC6–DDRC0
0
0
X
Input, Hi-Z⁽⁴⁾
DDRC6–DDRC0
X
1
X
Output
DDRC6–DDRC0
1. X = Don’t care
2. I/O pin pulled up to V_DD by internal pullup device.
3. Writing affects data register, but does not affect input.
4. Hi-Z = High impedance
Accesses to PTC
Read
Write
Pin
PTC6–PTC0⁽³⁾
Pin
PTC6–PTC0⁽³⁾
PTC6–PTC0
PTC6–PTC0
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 4
Freescale Semiconductor
163