MC68HC08AZ0 Datasheet, PDF (44/444 Pages) Motorola, Inc – Advance Information

Freescale Semiconductor, Inc.
EBI
Functional description
The user has two optional chip-select lines to define areas within the 64K
byte address range to be occupied by external devices. The range of
each address chip-select region can be modified by software. The
software option provides the user with a choice of regions as shown in
Figure 7.
MC68HC08AZ0
42
0000
CS0 (4K)
and
Internal
1000
CS1 (60K)
0000
CS0 (4K)
and
Internal
1000
CS0 (12K)
4000
CS1 (48K)
FFFF
FFFF
0000
CS0 (4K)
and
Internal
1000
CS0 (28k)
8000
CS1 (32K)
FFFF
0000
CS0 (4K)
and
Internal
1000
CS0 (44K)
C000
CS1 (16K)
FFFF
Figure 7 Software controlled chip-select combinations
CS1 is intended for program space as it always includes the vector
space. CS0 may be used for any purpose and is in effect equivalent to
CS1. Extending CS0 address space below $1000 allows the user to
place external devices (e.g. I/O) in unused address locations below
$1000 without the use of an external decoder (the CS0 pin would
otherwise be redundant). Internal accesses will always have priority.
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