ST6285 データシートの表示（PDF） - STMicroelectronics
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ST6285 Datasheet PDF : 76 Pages
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ST62T85B/E85B
MEMORY MAP (Cont’d)
Table 1. ST62E85B/T80B Program Memory 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-0FFB h
0FFCh-0FFDh
0FFEh-0FFFh
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
Note: OTP/EPROM devices can be programmed
with the development tools available from STMicro-
electronics (ST62E8X-EPB).
1.3.2.1 Program ROM Page Register (PRPR)
The PRPR register can be addressed like a RAM
location in the Data Space at the address CAh ;
nevertheless it is a write only register that cannot
be accessed with single-bit operations. This regis-
ter is used to select the 2-Kbyte ROM bank of the
Program Space that will be addressed. The
number of the page has to be loaded in the PRPR
register. Refer to the Program Space description
for additional information concerning the use of
this register. The PRPR register is not modified
when an interrupt or a subroutine occurs.
Care is required when handling the PRPR register
as it is write only. For this reason, it is not allowed
to change the PRPR contents while executing in-
terrupt service routine, as the service routine
cannot save and then restore its previous content.
This operation may be necessary if common rou-
tines and interrupt service routines take more than
2K bytes ; in this case it could be necessary to di-
vide the interrupt service routine into a (minor) part
in the static page (start and end) and to a second
(major) part in one of the dynamic pages. If it is im-
possible to avoid the writing of this register in inter-
rupt service routines, an image of this register
must be saved in a RAM location, and each time
the program writes to the PRPR it must write also
to the image register. The image register must be
written before PRPR, so if an interrpt occurs be-
tween the two instructions the PRPR is not af-
fected.
Program ROM Page Register (PRPR)
Address: CAh — Write Only
7
0
-
-
-
-
-
- PRPR1 PRPR0
Bits 2-7= Not used.
Bit 5-0 = PRPR1-PRPR0: Program ROM Select.
These two bits select the corresponding page to
be addressed in the lower part of the 4K program
address space as specified in Table 2.
This register is undefined on Reset. Neither read
nor single bit instructions may be used to address
this register.
Table 2. 8Kbytes Program ROM Page Register
Coding
PRPR1
X
0
0
1
1
PRPR0
X
0
1
0
1
PC bit 11 Memory Page
1
Static Page (Page 1)
0
Page 0
0
Page 1 (Static Page
0
Page 2
0
Page 3
1.3.2.2 Program Memory Protection
The Program Memory in OTP or EPROM devices
can be protected against external readout of mem-
ory by selecting the READOUT PROTECTION op-
tion in the option byte.
In the EPROM parts, READOUT PROTECTION
option can be disactivated only by U.V. erasure
that also results into the whole EPROM context
erasure.
Note: Once the Readout Protection is activated, it
is no longer possible, even for STMicroelectronics,
to gain access to the Program memory contents.
Returned parts with a protection set can therefore
not be accepted.
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