XC2200 Derivatives
System Units (Vol. 1 of 2)
Central Processing Unit (CPU)
User’s Manual
4-41
V2.1, 2008-08
CPUSV2_X, V2.2
4.7.2
Long Addressing Modes
Long addressing modes specify 24-bit addresses and, therefore, can access any word
or byte data within the entire address space. Long addresses can be specified in
different ways to generate the full 24-bit address:
•
Use one of the four Data Page Pointers (DPP registers):
The used 16-bit pointer
selects a DPP with bits 15 … 14, bits 13 … 0 specify the 14-bit data page offset (see
).
•
Select the used data page directly:
The data page is selected by a preceeding
EXTP(R) instruction, bits 13 … 0 of the used 16-bit pointer specify the 14-bit data
page offset.
•
Select the used segment directly:
The segment is selected by a preceeding
EXTS(R) instruction, the used 16-bit pointer specifies the 16-bit segment offset.
Note: Word accesses on odd byte addresses are not executed. A hardware trap will be
triggered.
Figure 4-13 Data Page Pointer Addressing
MCA04924
9
0
DPP
DPP3 - 11
DPP2 - 10
DPP1 - 01
DPP0 - 00
16-Bit Data Address
Selects DPP
23
15 14
0
Page
Page Offset
Segment
Segment Offset
Memory
255
254
1
0
X
FF'0000
H
FE'0000
H
01'0000
H
00'0000
H
0
15 14