ST6369 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST6369' PDF : 71 Pages View PDF
ST6369
MEMORY SPACES (Continued)
Data ROM Addressing. All the read-only data are
physically implemented in the ROM in which the
Program Space is also implemented. The ROM
therefore contains the program to be executed and
also the constants and the look-up tables needed
for the program. The locations of Data Space in
which the different constants and look-up tables
are addressed by the ST6369 Core can be consid-
ered as being a 64-byte window through which it is
possible to access to the read-only data stored in
the ROM. This window is located from the 40H ad-
dress to the 7FH address in the Data space and al-
lows the direct reading of the bytes from the 000H
address to the 03FH address in the ROM. All the
bytes of the ROM can be used to store either in-
structions or read-only data. Indeed, the window
can be moved by step of 64 bytes along the ROM
in writing the appropriate code in the Write-only
Data ROM Window register (DRWR, location
C9H). The effective address of the byte to be read
as a data in the ROM is obtained by the concatena-
tion of the 6 less significant bits of the address in
the Data Space (as less significant bits) and the
content of the DRWR (as most significant bits). So
when addressing location 40H of data space, and
0 is loaded in the DRWR, the physical addressed
location in ROM is 00H.
Figure 14. Data ROM Window Register
DWR
Data ROM Window Register
(C9H, Write Only)
D7 D6 D5 D4 D3 D2 D1 D0
DWR0 = Data ROM Window 0
DWR1 = Data ROM Window 1
DWR2 = Data ROM Window 2
DWR3 = Data ROM Window 3
DWR4 = Data ROM Window 4
DWR5 = Data ROM Window 5
DWR6 = Data ROM Window 6
UNUSED
DWR6-DWR0. These are the Data Rom Window
bits that correspond to the upper bits of data ROM
program space. This register is undefined after re-
set.
Note. Care is required when handling the DRWR as
it is write only. For this reason, it is not allowed to
change the DRWR contents while executing inter-
rupts drivers, as the driver cannot save and than re-
store its previous content. 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 location,
and each time the program writes the DRWR it
writes also the image register. The image register
must be written first, so if an interrupt occurs be-
tween the two instructions the DRWR register is not
affected.
Figure 15. Data ROM Window Memory Addressing
DATA ROM
13 12 11 10 9 8 7 6 5 4 3 2 1 0 PROGRAM SPACE ADDRESS
WINDOW REGISTER 7 6 5 4 3 2 1 0
READ
CONTENTS
(DWR)
5 4 3 2 1 0 DATA SPACE ADDRESS
01
40h-7Fh
IN INSTRUCTION
Example:
DWR=28h 0 0
10
10
00
0 10
110 0
DATA SPACE ADDRESS
1
59h
ROM
ADDRESS:A19h 0 0 1 0 1 0 0 0 0 1 1 0 0 1
12/67
®
VR01573B
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