Port D
READ DDRC ($0006)
WRITE DDRC ($0006)
DDRCx
PTCx
RESET
WRITE PTC ($0002)
READ PTC ($0002)
#
PTCx
# PTC0 has schmitt trigger input.
Figure 16-11. Port C I/O Circuit
When DDRCx is a logic 1, reading address $0002 reads the PTCx data latch. When 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 16-4 summarizes the operation of the port C pins.
Table 16-4. Port C Pin Functions
Accesses to DDRC
Read/Write
Accesses to PTC
DDRC
Bit
PTC Bit
I/O Pin Mode
Read
Pin
Write
X(1)
X
Input, Hi-Z(2)
Output
PTC[7:0](3)
PTC[7:0]
0
1
DDRC[7:0]
DDRC[7:0]
PTC[7:0]
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
16.5 Port D
Port D is an 8-bit special function port that shares all of its pins with the keyboard interrupt module.
16.5.1 Port D Data Register (PTD)
The port D data register contains a data latch for each of the eight port D pins.
Address:
$0003
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
PTD7
PTD6
PTD5
PTD4
PTD3
PTD2
PTD1
PTD0
Reset:
Unaffected by reset
KBI4 KBI3
Alternative Function:
KBI7
KBI6
KBI5
KBI2
KBI1
KBI0
Figure 16-12. Port D Data Register (PTD)
MC68HC908AP Family Data Sheet, Rev. 4
Freescale Semiconductor
267
FREESCALE [ Freescale ]
