MC68HC908AS32A Datasheet, PDF (156/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

Input/Output Ports
Figure 13-9 shows the port C I/O logic.
READ DDRC ($0006)
WRITE DDRC ($0006)
RESET
WRITE PTC ($0002)
DDRCx
PTCx
PTCx
READ PTC ($0002)
Figure 13-9. Port C I/O Circuit
When bit DDRCx is a 1, reading address $0002 reads the PTCx data latch. When bit DDRCx is a 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 13-3 summarizes the operation of the port C pins.
Table 13-3. Port C Pin Functions
Bit
Value
0
1
PTC
Bit
2
2
I/O Pin
Mode
Input, Hi-Z
Output
Accesses to DDRC
Read/Write
DDRC[2]
DDRC[2]
0
X
Input, Hi-Z
DDRC[4:0]
1
X
Output
DDRC[4:0]
X = don’t care
Hi-Z = high impedance
1. Writing affects data register, but does not affect input.
Accesses to PTC
Read
Write
Pin
PTC2
0
—
Pin
PTC[4:0]⁽¹⁾
PTC[4:0]
PTC[4:0]⁽¹⁾
MC68HC908AS32A Data Sheet, Rev. 2.0
156
Freescale Semiconductor