Maxim Integrated MAXQ7667 - Manual (Page 18)

MAXQ7667 MEMORY MAP (DEFAULT CONDITION, UPA = 0)
0x0000
0x8000
0x9000
0x800
DATA MEMORY
0 15
LOGICAL SPACE
0xFFFF
PHYSICAL PROGRAM
(P0)
UTILITY ROM
LOGICAL SPACE
0x0000
0x8000
0x4000
0xA000
0xFFFF
0xA800
0x9000
PROGRAM MEMORY
15 0
LOGICAL SPACE
PHYSICAL DATA
Figure 2-4. Pseudo-Von Neumann Memory Map (MAXQ7667 Default)
2.2.3.5 Pseudo-Von Neumann Memory Mapping
The MAXQ7667 supports a pseudo-Von Neumann memory structure that can merge program and data into a linear memory map. This
is accomplished by mapping the data memory into the program space or mapping program memory segment into the data space. In
all MAXQ processors the program memory ranges from x0000h to x7FFFh is the normal user code segment, followed by the utility ROM
segment. The uppermost part of the 64KWord memory is the logical area for data memory when accessed as a code segment.
The program memory is logically divided into four program pages, in all MAXQ processors:
• P0 contains the lower 16KWords (available in MAXQ7667),
• P1 contains the second 16KWords (not available in MAXQ7667),
• P2 contains the third 16KWords (not available in MAXQ7667), and
• P3 contains the fourth 16KWords (not available in MAXQ7667).
The MAXQ7667 only has 16K of P0 space and hence the focus will be on P0.
The logical mapping of physical program memory page(s) into data space depends upon two factors: physical memory currently in
use for program execution; and word/byte data memory access selection. If execution is from the utility ROM, physical program mem-
ory page (P0) can logically be mapped to the upper half of data memory space. If logical data memory is used for execution, physi-
cal program memory page can logically be mapped to the lower half of data memory space.
Figure 2-4 summarizes 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 MAXQ7667 default to word access mode (WBSn = 1).
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MAXQ7667 User’s Guide