MC908AZ32ACFUE Datasheet, PDF (254/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

I/O Ports
Figure 23-16 shows the port E I/O logic.
READ DDRE ($000C)
WRITE DDRE ($000C)
RESET
WRITE PTE ($0008)
DDREx
PTEx
PTEx
READ PTE ($0008)
Figure 23-16. Port E I/O Circuit
When bit DDREx is a logic 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a
logic 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 23-5 summarizes the operation of the port E pins.
Table 23-5. Port E Pin Functions
DDRE
PTE
Bit
Bit
I/O Pin
Mode
Accesses to
DDRE
Read/Write
0
X
Input, Hi-Z DDRE[7:0]
1
X
Output
DDRE[7:0]
X = don’t care
Hi-Z = high impedance
1. Writing affects data register, but does not affect input.
Accesses to PTE
Read
Pin
PTE[7:0]
Write
PTE[7:0]⁽¹⁾
PTE[7:0]
MC68HC908AZ32A Data Sheet, Rev. 2
254
Freescale Semiconductor