Datasheet

Bus Control and Input/Output
Registers
MC9S12DP256 — Revision 1.1
Bus Control and Input/Output
Registers
Not all registers are visible in the MC9S12DP256 memory map under
certain conditions.
In special peripheral mode the first 16 registers associated with bus
expansion are removed from the memory map.
In expanded modes, some or all of port A, port B, and port E are used
for expansion buses and control signals. In order to allow emulation of
the single-chip functions of these ports, some of these registers must be
rebuilt in an external port replacement unit. In any expanded mode, port
A, and port B, are used for address and data lines so registers for these
ports, as well as the data direction registers for these ports, are removed
from the on-chip memory map and become external accesses.
In any expanded mode, port E pins may be needed for bus control (e.g.,
ECLK, R/W
). To regain the single-chip functions of port E, the emulate
port E (EME) control bit in the MODE register may be set. In this special
case of expanded mode and EME set, PORTE and DDRE registers are
removed from the on-chip memory map and become external accesses
so port E may be rebuilt externally.
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
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