MC68HC08AS32 Datasheet, PDF (151/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

NOTE:
Avoid glitches on port E pins by writing to the port E data register before changing
data direction register E bits from 0 to 1.
Figure 11-16 shows the port E I/O logic.
READ DDRE ($000C)
WRITE DDRE ($000C)
RESET
WRITE PTE ($0008)
DDREx
PTEx
PTEx
READ PTE ($0008)
Figure 11-16. 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 11-5 summarizes the operation of the port E pins.
Table 11-5. 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]
MC68HC08AS32 — Rev. 4.1
Freescale Semiconductor
Data Sheet
151