MC908AZ32ACFUE Datasheet, PDF (249/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

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 23-10 shows the port C I/O logic.
READ DDRC ($0006)
WRITE DDRC ($0006)
RESET
WRITE PTC ($0002)
DDRCx
PTCx
PTCx
Port C
READ PTC ($0002)
Figure 23-10. 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 23-3 summarizes the operation of the port C pins.
Table 23-3. Port C Pin Functions
Bit
Value
PTC
Bit
I/O Pin
Mode
Accesses to
DDRC
Read/Write
0
2
Input, Hi-Z
DDRC[2]
1
2
Output
DDRC[2]
0
X
Input, Hi-Z DDRC[5:0]
1
X
Output
DDRC[5:0]
X = don’t care
Hi-Z = high impedance
1. Writing affects data register, but does not affect input.
Accesses to PTC
Read
Pin
0
Pin
PTC[5:0]
Write
PTC2
—
PTC[5:0]⁽¹⁾
PTC[5:0]
MC68HC908AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
249