ST6391 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST6391' PDF : 68 Pages View PDF
ST6391,92,93,95,97,99
MEMORY SPACES (Continued)
Data RAM/EEPROM/OSD RAM Addressing
In all members of the ST639x family 64 bytes of data
RAM are directly addressablein the data space from
80h to BFh addresses. The additional 192 bytes of
RAM, the 384 bytes of EEPROM , and the OSD
RAM can be addressed using the banks of 64
bytes located between addresses 00h and 3Fh.
The selection of the bank is done by programming
the Data RAM Bank Register (DRBR) located at
the E8h address of the Data Space. In this way
each bank of RAM, EEPROM or OSD RAM can se-
lect 64 bytes at a time. No more than one bank
should be set at a time.
Figure 18. Data RAM Bank Register
DRBR
Data RAM
Bank Register
(E8h, Write Only)
D7 D6 D5 D4 D3 D2 D1 D0
DRBR0
DRBR1
DRBR2
DRBR3
DRBR4
DRBR5
DRBR6
DRBR7
DRBR7,DRBR1,DRBR0. These bits select the
EEPROM pages.
DRBR6, DRBR5. Each of these bits, when set, will
select one OSD RAM register page.
DRBR4,DRBR3,DRBR2. Each of these bits, when
set, will select one RAM page.
This register is undefined after reset.
Table 5 summarizes how to set the Data RAM
Bank Register in order to select the various banks
or pages.
Note :
Care is required when handling the DRBR as it is
write only. For this reason, it is not allowed to
change the DRBR contents while executing inter-
rupts drivers, as the driver cannot save and than
restore its previous content. 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, and each time the program writes
the DRBR it writes also the image register.
The image register must be written first, so if an in-
terrupt occurs between the two instructions the
DRBR is not affected.
Table 5. Data RAM Bank Register Set-up
Hex.
01h
02h
03h
81h
82h
83h
04h
08h
10h
20h
40h
DRBR Value
Binary
0000 0001
0000 0010
0000 0011
1000 0001
1000 0010
1000 0011
0000 0100
0000 1000
0001 0000
0010 0000
0100 0000
Selection
EEPROM Page 0
EEPROM Page 1
EEPROM Page 2
EEPROM Page 3
EEPROM Page 4
EEPROM Page 5
RAM Page 2
RAM Page 3
RAM Page 4
OSD Page 5
OSD Page 6
All devices
ST6395 and ST6397
ONLY
All devices
15/64
®
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