mc68hc908gp32 Freescale Semiconductor, Inc, mc68hc908gp32 Datasheet - Page 128

• Manufacturer Part Number: mc68hc908gp32
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports
RxD — SCI Receive Data Input
TxD — SCI Transmit Data Output
12.6.2 Data Direction Register E
Data direction register E (DDRE) determines whether each port E pin is an input or an output. Writing a
logic 1 to a DDRE bit enables the output buffer for the corresponding port E pin; a logic 0 disables the
output buffer.
DDRE1 and DDRE0 — Data Direction Register E Bits
Figure 12-19
128
The PTE1/RxD pin is the receive data input for the SCI module. When the enable SCI bit, ENSCI, is
clear, the SCI module is disabled, and the PTE1/RxD pin is available for general-purpose I/O. See
Chapter 13 Serial Communications Interface Module
The PTE0/TxD pin is the transmit data output for the SCI module. When the enable SCI bit, ENSCI, is
clear, the SCI module is disabled, and the PTE0/TxD pin is available for general-purpose I/O. See
Chapter 13 Serial Communications Interface Module
These read/write bits control port E data direction. Reset clears DDRE1 and DDRE0, configuring all
port E pins as inputs.
1 = Corresponding port E pin configured as output
0 = Corresponding port E pin configured as input
shows the port E I/O logic.
Address:
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.
Reset:
Read:
Write:
READ DDRE ($000C)
WRITE DDRE ($000C)
WRITE PTE ($0008)
READ PTE ($0008)
$000C
Bit 7
0
0
Figure 12-18. Data Direction Register E (DDRE)
= Unimplemented
6
0
0
RESET
MC68HC908GP32 Data Sheet, Rev. 10
Figure 12-19. Port E I/O Circuit
5
0
0
NOTE
DDREx
PTEx
4
0
0
(SCI).
(SCI).
3
0
0
2
0
0
DDRE1
1
0
Freescale Semiconductor
DDRE0
Bit 0
PTEx
0