ST62T30B ST62E30B
1.3 MEMORY MAP
1.3.1 Introduction
The MCU operates in three separate memory
spaces: Program space, Data space, and Stack
space. Operation in these three memory spaces is
described in the following paragraphs.
Briefly, Program space contains user program
code in Program memory and user vectors; Data
space contains user data in RAM and in Program
memory, and Stack space accommodates six lev-
els of stack for subroutine and interrupt service
routine nesting.
1.3.2 Program Space
Program Space comprises the instructions to be
executed, the data required for immediate ad-
dressing mode instructions, the reserved factory
test area and the user vectors. Program Space is
addressed via the 12-bit Program Counter register
(PC register).
Program Space is organised in four 2K pages.
Three of them are addressed in the 000h-7FFh lo-
cations of the Program Space by the Program
Counter and by writing the appropriate code in the
Program ROM Page Register (PRPR register). A
Figure 4. Memory Addressing Diagram
PROGRAM SPACE
DATA SPACE
common (STATIC) 2K page is available all the
time for interrupt vectors and common subrou-
tines, independently of the PRPR register content.
This “STATIC” page is directly addressed in the
0800h-0FFFh by the MSB of the Program Counter
register PC 11. Note this page can also be ad-
dressed in the 000-7FFh range. It is two different
ways of addressing the same physical memory.
Jump from a dynamic page to another dynamic
page is achieved by jumping back to the static
page, changing contents of PRPR and then jump-
ing to the new dynamic page.
Figure 3. 8Kbytes Program Space Addressing
ROM SPACE
PC
SPACE
000h
Page 0
7FFh
800h
FFFh
Page 1
Static
Page
0000h
Page 1
Static
Page
Page 2
1FFFh
Page 3
0000h
000h
RAM / EEPROM
BANKING AREA
0-63
03Fh
040h
DATA READ-ONLY
MEMORY WINDOW
07Fh
080h
081h
082h
083h
084h
0C0h
X REGISTER
Y REGISTER
V REGISTER
W REGISTER
RAM
DATA READ-ONLY
MEMORY
WINDOW SELECT
DATA RAM
BANK SELECT
ACCUMULATOR
VR01568
PROGRAM
MEMORY
0FF0h
INTERRUPT &
RESET VECTORS
0FFFh
0FFh
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