MC68HC908EY16 Datasheet, PDF (122/278 Pages) Motorola, Inc – Microcontrollers

Input/Output (I/O) Ports (PORTS)
Figure 12-12 shows the port D I/O logic.
READ DDRD ($0007)
WRITE DDRD ($0007)
RESET
WRITE PTD ($0003)
DDRDx
PTDx
PTDx
READ PTD ($0003)
Figure 12-12. Port D I/O Circuit
When bit DDRDx is a 1, reading address $0003 reads the PTDx data latch. When bit DDRDx is a 0,
reading address $0003 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 12-4 summarizes the operation of the port D pins.
Table 12-4. Port D Pin Functions
DDRD
Bit
PTD
Bit
I/O Pin
Mode
Accesses to DDRD
Read/Write
0
X
Input, Hi-Z
DDRD[1:0]
1
X
Output
DDRD[1:0]
X = don’t care
Hi-Z = high impedance
1. Writing affects data register, but does not affect input.
Accesses to PTD
Read
Write
Pin
PTD[1:0]⁽¹⁾
PTD[1:0]
PTD[1:0]
12.6 Port E
Port E is a 2-bit special function port that shares its pins with the enhanced serial communications
interface module (ESCI).
12.6.1 Port E Data Register
The port E data register contains a data latch for each of the port E pins.
Address: $0008
Bit 7
6
Read: 0
0
Write:
Reset:
Alternative Function:
5
4
3
2
0
0
0
0
Unaffected by reset
= Unimplemented
Figure 12-13. Port E Data Register (PTE)
1
PTE1
Bit 0
PTE0
RXD
TXD
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
122
Freescale Semiconductor