Maxim Integrated MAXQ622 - Manual (Page 16)

MAXQ612/MAXQ622 User’s Guide
2-12 Maxim Integrated
Figure 2-6. CPA Impact on Code Pointer Access of Program Memory
2.5.2 Memory Mapping into Code Space
The effective program address can be anywhere in the full 128KB memory space . Program memory from 0000h to
FFFFh is the normal user code segment, followed by the utility ROM . The top of the memory is the logical area for data
memory when accessed as a code segment . Pages P2, P3 of the program memory are not accessible for program
execution by default . These pages need to be activated by user software . The upper program access (UPA) bit must
be set to 1 to activate P2 and P3 . Once UPA is set, P2 and P3 occupy the upper half of the program space, and utility
ROM and physical data memory can be accessed as data only . Figure 2-7 summarizes UPA effect .
Table 2-3. CPA Access of Program Data with Code Pointer
CODE POINTER MAP PHYSICAL PROGRAM MEMORY
15 0
CODE POINTER ACCESS OF WORD MODE MEMORY MAP
CODE POINTER OF BYTE MODE MEMORY MAP
CODE POINTER MAP
15 0 0 7
15 0
PHYSICAL PROGRAM MEMORY
PHYSICAL PROGRAM (P3)
PHYSICAL PROGRAM (P2)
PHYSICAL PROGRAM (P1)
PHYSICAL PROGRAM (P0)
PHYSICAL PROGRAM (P2)
CPA = 1
CPA = 0
PHYSICAL PROGRAM (P3)
PHYSICAL PROGRAM (P1)
PHYSICAL PROGRAM (P0)
PHYSICAL PROGRAM (P3)
PHYSICAL PROGRAM (P2)
PHYSICAL PROGRAM (P1)
PHYSICAL PROGRAM (P0)
x0000
xFFFF
x0000
xFFFF
x0000
xFFFF
x0000
xFFFF
CPA BYTE MODE ACCESS WORD MODE ACCESS
0 Lower 64KB Don’t care/no effect
1 Upper 64KB Don’t care/no effect