MC68HC11PH8 Datasheet, PDF (61/264 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

PH8.DS03/Modes+mem
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[DS97 v 4.1] 08/Apr/97@13:55
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REG[3:0] — 128-byte register block position
These four bits specify the upper hexadecimal digit of the address for the 128-byte block of internal
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registers. The register block is positioned at the beginning of any 4K page in the memory map.
Refer to Table 3-5.
Table 3-5 RAM and register remapping
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RAM[3:0]
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Location
$0000Ð$07FF
$1000Ð$17FF
$2000Ð$27FF
$3000Ð$37FF
$4000Ð$47FF
$5000Ð$57FF
$6000Ð$67FF
$7000Ð$77FF
$8000Ð$87FF
$9000Ð$97FF
$A000Ð$A7FF
$B000Ð$B7FF
$C000Ð$C7FF
$D000Ð$D7FF
$E000Ð$E7FF
$F000Ð$F7FF
REG[3:0] Location
0000 $0000Ð$007F
0001 $1000Ð$107F
0010 $2000Ð$207F
0011 $3000Ð$307F
0100 $4000Ð$407F
0101 $5000Ð$507F
0110 $6000Ð$607F
0111 $7000Ð$707F
1000 $8000Ð$807F
1001 $9000Ð$907F
1010 $A000Ð$A07F
1011 $B000Ð$B07F
1100 $C000Ð$C07F
1101 $D000Ð$D07F
1110 $E000Ð$E07F
1111 $F000Ð$F07F
When the memory map has the 128-byte register block mapped at the same location as RAM, the
registers have priority and the RAM is relocated to the memory space immediately following the
register block. This mapping feature keeps all the RAM available for use. Refer to Figure 3-3, which
illustrates the overlap.
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5
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7
8
9
10
$x000
$x07F
$x080
RAM A
$x000
$x07F
Register block
$x080
RAM B
RAM B
$x7FF
$x7FF
$x800
$x87F
RAM A
Register and RAM mapped
to different 4K boundaries.
Register and RAM mapped
to the same 4K boundary.
Figure 3-3 RAM and register overlap
MC68HC11PH8
OPERATING MODES AND ON-CHIP MEMORY
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¬^TPG
MOTOROLA
3-15
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