MC908AB32CFUE Datasheet, PDF (328/392 Pages) Freescale Semiconductor, Inc – Microcontrollers

Input/Output (I/O) Ports
17.7.2 Data Direction Register E (DDRE)
Data direction register E 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.
Address: $000C
Bit 7
Read:
DDRE7
Write:
Reset: 0
6
DDRE6
0
5
DDRE5
0
4
DDRE4
0
3
DDRE3
0
2
DDRE2
0
1
DDRE1
0
Figure 17-16. Data Direction Register E (DDRE)
Bit 0
DDRE0
0
DDRE[7:0] — Data Direction Register E Bits
These read/write bits control port E data direction. Reset clears
DDRE[7:0], 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 17-17 shows
the port E I/O logic.
READ DDRE ($000C)
WRITE DDRE ($000C)
RESET
WRITE PTE ($0008)
DDREx
PTEx
PTEx
READ PTE ($0008)
Figure 17-17. Port E I/O Circuit
Technical Data
328
Input/Output (I/O) Ports
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor