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MC908QC8CDRE Datasheet(Hoja de datos) 42 Page - Freescale Semiconductor, Inc

No. de Pieza. MC908QC8CDRE
Descripción  M68HC08 Microcontrollers
Descarga  274 Pages
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Fabricante  FREESCALE [Freescale Semiconductor, Inc]
Página de inicio  http://www.freescale.com
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 42 page
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Memory
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 5
42
Freescale Semiconductor
Figure 2-6. FLASH Block Protect Start Address
2.6.7 EEPROM Memory Emulation Using FLASH Memory
In some applications, the user may want to repeatedly store and read a set of data from an area of
nonvolatile memory. This is easily implemented in EEPROM memory because single byte erase is
allowed in EEPROM.
When using FLASH memory, the minimum erase size is a page. However, the FLASH can be used as
EEPROM memory. This technique is called “EEPROM emulation”.
The basic concept of EEPROM emulation using FLASH is that a page is continuously programmed with
a new data set without erasing the previously programmed locations. Once the whole page is completely
programmed or the page does not have enough bytes to program a new data set, the user software
automatically erases the page and then programs a new data set in the erased page.
In EEPROM emulation when data is read from the page, the user software must find the latest data set
in the page since the previous data still remains in the same page. There are many ways to monitor the
page erase timing and the latest data set. One example is unprogrammed FLASH bytes are detected by
checking programmed bytes (non-$FF value) in a page. In this way, the end of the data set will contain
unprogrammed data ($FF value).
A couple of application notes, describing how to emulate EEPROM using FLASH, are available on our
web site. Titles and order numbers for these application notes are given at the end of this subsection.
Table 2-2. Examples of Protect Start Address
BPR[7:0]
Start of Address of Protect Range(1)
1. The end address of the protected range is always $FFFF.
$00(2)
2. $BE00–$BFFF is always protected unless the entire FLASH memory is un-
protected, BPR[7:0] = $FF.
The entire FLASH memory is protected.
$01 (0000 0001)
$C040 (1100 0000 0100 0000)
$02 (0000 0010)
$C080 (1100 0000 1000 0000)
$03 (0000 0011)
$C0C0 (1100 0000 1100 0000)
and so on...
$FD (1111 1101)
$FF40 (1111 1111 0100 0000)
$FE (1111 1110)
$FF80 (1111 1111 1000 0000)
$FF
The entire FLASH memory is not protected.
0
0
0
0
0
1
1
FLBPR VALUE
START ADDRESS OF
16-BIT MEMORY ADDRESS
FLASH BLOCK PROTECT
0




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