Datasheet

Bus Control and Input/Output
Registers
MC68HC912DT128A — Rev 4.0 Technical Data
MOTOROLA Bus Control and Input/Output 107
(R/W), IRQ, and XIRQ. When the associated pin is not used for one
of these specific functions, the pin can be used as general-purpose
I/O. The port E assignment register (PEAR) selects the function of
each pin. DDRE determines the primary direction of each port E pin
when configured to be general-purpose I/O.
Some of these pins have software selectable pull-ups (DBE
, LSTRB,
R/W
, IRQ and XIRQ). A single control bit enables the pull-ups for all
these pins which are configured as inputs.
This register is not in the map in peripheral mode or expanded modes
when the EME bit is set.
Read and write anytime.
This register determines the primary direction for each port E pin
configured as general-purpose I/O.
0 = Associated pin is a high-impedance input
1 = Associated pin is an output
PE[1:0] are associated with XIRQ
and IRQ and cannot be configured
as outputs. These pins can be read regardless of whether the
alternate interrupt functions are enabled.
This register is not in the map in peripheral mode and expanded
modes while the EME control bit is set.
Read and write anytime.
DDRE — Port E Data Direction Register $0009
Bit 7654321Bit 0
DDE7 DDE6 DDE5 DDE4 DDE3 DDE2 0 0
RESET: 00000000
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cale Semiconductor,
I
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