MC68HC908EY16 Datasheet, PDF (124/278 Pages) Motorola, Inc – Microcontrollers

Input/Output (I/O) Ports (PORTS)
Figure 12-15 shows the port E I/O logic.
READ DDRE ($000A)
WRITE DDRE ($000A)
RESET
WRITE PTE ($0008)
DDREx
PTEx
PTEx
READ PTE($0008)
Figure 12-15. Port E I/O Circuit
When bit DDREx is a 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a 0,
reading address $0008 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 12-5 summarizes the operation of the port E pins.
Table 12-5. Port E Pin Functions
DDRE PTE
Bit
Bit
I/O Pin
Mode
Accesses to DDRE
Read/Write
0
X
Input, Hi-Z
DDRE[1:0]
1
X
Output
DDRE[1:0]
X = don’t care
Hi-Z = high impedance
1. Writing affects data register, but does not affect input.
Accesses to PTE
Read
Write
Pin
PTE[1:0]⁽¹⁾
PTE[1:0]
PTE[1:0]
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
124
Freescale Semiconductor