MC68HC908GT16_07 FREESCALE [Freescale Semiconductor, Inc], MC68HC908GT16_07 Datasheet - Page 136

• Manufacturer Part Number: MC68HC908GT16_07
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Input/Output (I/O) Ports (PORTS)
DDRE4–DDRE0 — Data Direction Register E Bits
Figure 12-19
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.
136
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
These read/write bits control port E data direction. Reset clears DDRE4–DDRE0, configuring all port
E pins as inputs.
DDRE
Bit
0
1
1 = Corresponding port E pin configured as output
0 = Corresponding port E pin configured as input
shows the port E I/O logic.
PTE
Address:
X
Bit
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.
X
(1)
Reset:
Read:
Write:
MC68HC908GT16 • MC68HC908GT8 • MC68HC08GT16 Data Sheet, Rev. 5.0
READ DDRE ($000C)
WRITE DDRE ($000C)
WRITE PTE ($0008)
READ PTE ($0008)
$000C
Bit 7
Input, Hi-Z
0
0
Figure 12-18. Data Direction Register E (DDRE)
I/O Pin
Output
Mode
= Unimplemented
(2)
6
0
0
Table 12-6. Port E Pin Functions
RESET
Figure 12-19. Port E I/O Circuit
5
0
0
Accesses to DDRE
DDRE4–DDRE0
DDRE4–DDRE0
Table 12-6
Read/Write
NOTE
DDRE4
DDREx
PTEx
4
0
summarizes the operation of the port E pins.
DDRE3
3
0
DDRE2
PTE4–PTE0
2
0
Read
Pin
DDRE1
Accesses to PTE
1
0
Freescale Semiconductor
DDRE0
Bit 0
PTEx
0
PTE4–PTE0
PTE4–PTE0
Write
(3)