Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
318 Input/Output (I/O) Ports MOTOROLA
Input/Output (I/O) Ports
15.7.2 Data Direction Register E
Data direction register E (DDRE) determines whethe r each po rt E pin is
an input or an output. Writing a logic 1 to a D DRE bit enable s the out put
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 regi ster before
changing data direction register E bits from 0 to 1.
Figure 15-15 shows the port E I/O logic.
Figure 15-15. Port E I/O Circuit
Address: $000C
Bit 7654321Bit 0
Read: DDRE7 DDRE6 DDRE5 DDRE4 DDRE3 DDRE2 DDRE1 DDRE0
Write:
Reset:00000000
Figure 15-14. Data Direction Register E (DDRE)
READ DDRE ($000C)
WRITE DDRE ($000C)
RESET
WRITE PTE ($0008)
READ PTE ($0008)
PTEx
DDREx
PTEx
INTERNAL DATA BUS