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ST63126 View Datasheet(PDF) - STMicroelectronics

Part Name
Description
MFG CO.
'ST63126' PDF : 86 Pages View PDF
ST63140,142,126,156
MEMORY SPACES
The MCUs operate in three different memory
spaces: Program Space, Data Space, and Stack
Space. A description of these spaces is shown in
the following Figures.
Program Space
The program space is physically implemented in
the ROM and includes all the instructions that are
to be executed, as well as the data required for the
immediate addressing mode instructions, the re-
served test area and user vectors. It is addressed
thanks to the 12-bit Program Counter register (PC
register) and so, the ST631xx Core can directly ad-
dress up to 4K bytes of Program Space. Neverthe-
less, the Program Space can be extended by the
addition of 2-Kbyte ROM banks as it is shown in
Figure 8 in which the 8K bytes memory is de-
scribed.
These banks are addressed by pointing to the
000h-7FFh locations of the Program Space thanks
to the Program Counter, and by writing the appro-
priate code in the Program ROM Page Register
(PRPR) located at address CAh of the Data
Space. Because interrupts and common subrou-
tines should be available all the time only the lower
2K bytes of the 4K program space are bank
switched while the upper 2K bytes can be seen as
static space. Table 3 gives the codes that allow the
selection of the corresponding banks.
Note that, from the memory point of view, the Page
1 and the Static Page represent the same physical
memory: it is only a different way of addressing the
same location. On the ST631xx a total of 8192
bytes of ROM have been implemented; 7948 are
available as user ROM while 244 are reserved for
testing.
Figure 8. ST631xx 8K Bytes Program Space
Addressing Description
Program
counter
space
0000h
0FFFh
Static Page
Page 1
0800h
07FFh
Page 0
Page 1
Static Page
0000h
1FFFh
Page 2
Page 3
Figure 7. ST631xx Memory Addressing Description Diagram
STACK SPAC E
PROGRAM SPACE
DATA SPACE
PROGRAM COUNTER
STACK LEVEL 1
STACK LEVEL 2
STACK LEVEL 3
STACK LEVEL 4
STACK LEVEL 5
STACK LEVEL 6
0000h
ROM
07FFh
0800h
ROM
0FF0h
0FFFh
INTERRUPT &
RESET VEC TOR S
10/82
®
0-63
000h
RAM / EEPROM
BANKING AREA
03Fh
040h
070h
080h
081h
082h
083h
084h
0C 0h
DATA ROM
WINDOW
X REGISTER
Y REGISTER
V REGISTER
W REGISTER
RAM
DATA ROM
WIND OW SELECT
DATA RAM
BANK SELECT
0FFh AC CUMUL ATOR
VR001568
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