ST62T35B ST Microelectronics, ST62T35B Datasheet - Page 8

• Manufacturer Part Number: ST62T35B
• Description: (ST62E35B / ST62T35B) 8-BIT OTP/EPROM MCUs
• Manufacturer: ST Microelectronics

ST62T35B/E35B
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
8/82
7
0000h
0FF0h
0FFFh
RESET VECTORS
INTERRUPT &
PROGRAM
MEMORY
PROGRAM SPACE
0-63
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
PC
SPACE
000h
7FFh
800h
FFFh
0C0h
0FFh
03Fh
07Fh
000h
040h
080h
081h
082h
083h
084h
Page 0
0000h
Page 1
Static
Page
MEMORY
DATA READ-ONLY
DATA READ-ONLY
WINDOW SELECT
W REGISTER
X REGISTER
Y REGISTER
V REGISTER
ACCUMULATOR
ROM SPACE
BANK SELECT
RAM / EEPROM
BANKING AREA
Page 1
DATA RAM
Static
Page
MEMORY
RAM
WINDOW
DATA SPACE
Page 2
Page 3
1FFFh
VR01568