Input/Output (I/O) Ports
Technical Data MC68HC908AB32 — Rev. 1.0
328 Input/Output (I/O) Ports MOTOROLA
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.
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.
Figure 17-17. Port E I/O Circuit
Address: $000C
Bit 7 654321Bit 0
Read:
DDRE7 DDRE6 DDRE5 DDRE4 DDRE3 DDRE2 DDRE1 DDRE0
Write:
Reset: 0 0000000
Figure 17-16. Data Direction Register E (DDRE)
READ DDRE ($000C)
WRITE DDRE ($000C)
RESET
WRITE PTE ($0008)
READ PTE ($0008)
PTEx
DDREx
PTEx
INTERNAL DATA BUS
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