MC68HC908GT16 Datasheet, PDF (247/412 Pages) Motorola, Inc – Microcontrollers

Input/Output (I/O) Ports
Port E
DDRE4–DDRE0 — Data Direction Register E Bits
These read/write bits control port E data direction. Reset clears
DDRE4–DDRE0, configuring all port E pins as inputs.
1 = Corresponding port E pin configured as output
0 = Corresponding port E pin configured as input
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 16-19 shows the port E I/O logic.
READ DDRE ($000C)
WRITE DDRE ($000C)
RESET
WRITE PTE ($0008)
DDREx
PTEx
PTEx
READ PTE ($0008)
Figure 16-19. 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 16-6 summarizes
the operation of the port E pins.
Table 16-6. Port E Pin Functions
DDRE PTE
Bit Bit
I/O Pin
Mode
Accesses
to DDRE
Read/Write
Accesses
to PTE
Read
Write
0
X⁽¹⁾ Input, Hi-Z^{(2) DDRE4–DDRE0}
Pin
PTE4–PTE0⁽³⁾
1
X
Output
DDRE4–DDRE0 PTE4–PTE0 PTE4–PTE0
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
MOTOROLA
Input/Output (I/O) Ports
Technical Data
247