ST6381B4/XXX データシートの表示（PDF） - STMicroelectronics
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ST6381B4/XXX Datasheet PDF : 82 Pages
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ST6380, ST6381, ST6382, ST6383, ST6388, ST6389
MEMORY SPACES (Cont’d)
Program ROM Page Register (PRPR)
Address: CAh - Write only
Reset Value: XXh
7
0
-
-
-
- PRPR3 PRPR2 PRPR1 PRPR0
D7-D4. These bits are not used but have to be
written to “0”.
PRPR3-PRPR0. These are the program ROM
banking bits and the value loaded selects the cor-
responding page to be addressed in the lower part
of 4K program address space as specified in Table
4. This register is undefined on reset.
Caution: This register contains at least one write
only bit. Single bit instructions (SET, RES, INC
and DEC) should not be used.
Note. Only the lower part of address space has
been bankswitched because interrupt vectors and
common subroutines should be available all the
time. The reason of this structure is due to the fact
that it is not possible to jump from a dynamic page
to another, unless jumping back to the static page,
changing contents of PRPR and then jumping to a
different dynamic page.
Care is required when handling the PRPR as it is
write only. For this reason, it is not allowed to
change the PRPR contents while executing inter-
rupts drivers, as the driver cannot save and than
Table 4. Program Memory Map
restore its previous content. Anyway, this opera-
tion may be necessary if the sum of common rou-
tines and interrupt drivers will take more than 2K
bytes; in this case it could be necessary to divide
the interrupt driver in a (minor) part in the static
page (start and end), and in the second (major)
part in one dynamic page. If it is impossible to
avoid the writing of this register in interrupts driv-
ers, an image of this register must be saved in a
RAM location. Each time the program writes the
PRPR register, the image register should also be
written. The image register must be written first, so
if an interrupt occurs between the two instructions
the PRPR is not affected.
Table 3. Program Memory Page Register coding
PRPR3 PRPR2 PRPR1 PRPR0 PC11 Memory Page
X
X
X
X
1
Static Page
(Page 1)
0
0
0
0
0 Page 0
0
0
0
1
0
Page 1 (Static
Page)
0
0
1
0
0 Page 2
0
0
1
1
0 Page 3
0
1
0
0
0 Page 4
0
1
0
1
0 Page 5
0
1
1
0
0 Page 6
0
1
1
1
0 Page 7
1
0
0
0
0 Page 8
1
0
0
1
0 Page 9
Program Memory Page
PAGE 0
PAGE 1
“STATIC”
PAGE 2
PAGE 3
PAGE 4
PAGE 5
PAGE 6
PAGE 7
PAGE 8
PAGE 9
Device Address
0000h-007Fh
0080h-07FFh
0800h-0F9Fh
0FA0h-0FEFh
0FF0h-0FF7h
0FF8h-0FFBh
0FFCh-0FFDh
0FFEh-0FFFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
0000h-000Fh
0010h-07FFh
Description
Reserved
User ROM
User ROM
Reserved
Interrupt Vectors
Reserved
NMI Vector
Reset Vector
Reserved
User ROM
Reserved
User ROM (End of 8K ST6380, 81)
Reserved
User ROM
Reserved
User ROM
Reserved
User ROM
Reserved
User ROM (End of 16K ST6382, 83)
Reserved
User ROM
Reserved
User ROM (End of 20K ST6388, 89)
10/82
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