MC68HC908JW32_09 Datasheet, PDF (181/232 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Figure 13-16 shows the port E I/O circuit logic.
READ DDRE ($0009)
WRITE DDRE ($0009)
RESET
WRITE PTE ($0008)
DDREx
PTEx
Port E
PTEx
READ PTE ($0008)
Figure 13-16. Port E I/O Circuit
When bit DDREx is a logic 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a
logic 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. Table 13-5 summarizes the operation of the port E pins.
Table 13-9. Port E Pin Functions
DDRE
Bit
Accesses
PTE
Bit
I/O Pin Mode
to DDRE
Read/Write
0
X⁽¹⁾
Input, Hi-Z⁽²⁾
DDRE[7:2]
1
X
Output
DDRE[7:2]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
Accesses to PTE
Read
Pin
PTE[7:2]
Write
PTE[7:2]⁽³⁾
PTE[7:2]
MC68HC908JW32 Data Sheet, Rev. 6
Freescale Semiconductor
181