ST6369 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST6369' PDF : 71 Pages View PDF
ST6369
MEMORY SPACES (Continued)
Figure 11. Program ROM Page Register
PRPR
Program ROM Page Register
(CAH, Write Only)
D7 D6 D5 D4 D3 D2 D1 D0
PRPR0
PRPR1
UNUSED
UNUSED
UNUSED
D7-D2. These bits are not used but have to be writ-
ten to “0”.
PRPR1-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
3. This register is undefined on reset.
Table 3. Program ROM Page Register Coding
PRPR1 PRPR0
X
X
0
0
0
1
1
0
1
1
PC11
1
0
0
0
0
Memory
Page
Static Page (Page 1)
Page 0
Page 1
(Static Page)
Page 2
Page 3
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
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 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 drivers, an im-
age of this register must be saved in a RAM loca-
tion, and each time the program writes the PRPR it
writes also the image register. The image register
must be written first, so if an interrupt occurs be-
tween the two instructions the PRPR is not af-
fected.
Table 4. ST6369 Program ROM Map
ROM Page
PAGE 0
PAGE 1
“STATIC”
PAGE 2
PAGE 3
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
10/67
®
Description
Reserved
User ROM
User ROM
Reserved
Interrupt Vectors
Reserved
NMI Vector
Reset Vector
Reserved
User ROM
Reserved
User ROM
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