ST6369 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST6369' PDF : 71 Pages View PDF
ST6369
MEMORY SPACES
The MCUs operate in three different memory
spaces: Stack Space, Program Space and Data
Space. A description of these spaces is shown in
Figure 9.
Stack Space
The stack space consists of six 12 bit registers that
are used for stacking subroutine and interrupt return
addressesplus the current programcounterregister.
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 ST6369 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 11 in which a 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
appropriate code in the Program ROM Page Reg-
ister (PRPR) located at the CAH address of the
Data Space. Because interrupts and common sub-
routines should be available all the time only the
lower 2K byte of the 4K program space are bank
switched while the upper 2K byte can be seen as
static space. Table 3 gives the different codes that
allows 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.
Figure 10. 8K Bytes Program Space Address-
ing Description
Program
counter 0000H
space
0FFFH
Static Page
Page 1
0800H
07FFH
0000H
Page 0
Page 1
Static Page
1FFFH
Page 2
Page 3
Figure 9. Memory Addressing Description Diagram
STACK SPACE
PROGRAM SPACE
DATA SPACE
PROGRAM COUNTER
STACK LEVE L 1
STACK LEVE L 2
STACK LEVE L 3
STACK LEVE L 4
STACK LEVE L 5
STACK LEVE L 6
0000h
ROM
07FFh
0800h
ROM
0FF0h
0 FFF h
INTERRUPT &
RESET VECTORS
0-63
000h
RAM / EEPROM
BANKING AREA
03Fh
040h
D ATA ROM
WINDOW
070h
080h
081h
082h
083h
084h
0C0h
X REGISTER
Y REGISTER
V REGISTER
W R EGIST ER
RAM
DA TA R OM
W IND OW SELE CT
D ATA R AM
BA N K S EL EC T
0FFh AC CUMUL ATOR
VR001568
9/67
®
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