Maxim Integrated MAXQ Family - Manual (Page 13)

2-8
MAXQ Family User’s Guide
page (16kWords) may be logically mapped, as just defined, to either the upper or lower half of data memory. If word access mode is
selected, two pages (32kWords total) may be logically mapped to data memory. To avoid memory overlapping in the byte access
mode, the physical data memory should be confined to the address range x0000h to x3FFFh in word mode. The selection of physical
memory page or pages to be logically mapped to data space is determined by the Code Access Bits (CDA1:0):
Figure 2-3 and Figure 2-4 summarize the default memory maps for this memory structure. The primary difference lies in the reset default
settings for the data pointer Word/Byte Mode Select (WBSn) bits. The WBSn bits of the MAXQ10 default to byte access mode (WBSn
= 0), while the MAXQ20 WBSn bits default to word access mode (WBSn = 1).
CDA1:0 SELECTED PAGE IN BYTE MODE
SELECTED PAGE IN
WORD MODE
00 P0 P0 and P1
01 P1 P0 and P1
10 P2 P2 and P3
11 P3 P2 and P3
PHYSICAL PROGRAM
(P0)
UTILITY ROM
PHYSICAL DATA
x0000
x8000
xA000
xFFFF
x0000
x8000
xFFFF
DATA MEMORY PROGRAM MEMORY
15 0 0 7
LOGICAL SPACE
LOGICAL SPACE
MAXQ10 MEMORY MAP (DEFAULT CONDITION)
PHYSICAL PROGRAM
(P1)
Figure 2-3. Pseudo Von Neumann Memory Map (MAXQ10 Default)
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