AN2153 Freescale Semiconductor / Motorola, AN2153 Datasheet - Page 12

• Manufacturer Part Number: AN2153
• Description: A Serial Bootloader for Reprogramming the MC9S12DP256 FLASH Memory
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
FLASH Erasure
12
As previously discussed, each 64-K block is organized in 1024 rows of
32 words. An erase sector contains 8 rows or 512 bytes. Erase
operations may be performed on a sector as small as 512 bytes or on
the entire 65,536 byte block. An erased word reads $FFFF and a
programmed word reads $0000. Program and erase operations are very
similar, differing only in the command written to the FCMD register and
the data written to the FLASH memory array. The FLASH state machine
erase and verify command operation is depicted in the flowchart of
Figure
Before beginning either an erase or program operation, it is necessary
to write a value to the FCLKDIV register. The value written to the
FCLKDIV register programs a down counter used to divide the oscillator
clock, producing a 150-kHz to 200-kHz clock source used to drive the
FLASH memory’s state machine. The most significant bit of the
FCLKDIV register, when set, indicates that the register has been
Freescale Semiconductor, Inc.
TO FCMD REGISTER
WRITE BKSEL[1:0]
WRITE COMMAND
WRITE ALIGNED
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WRITE PPAGE
DATA WORD
REGISTER
7.
CBEIF
FLAG
BITS
SET
?
YES
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Figure 7. Erase and Verify Flowchart
NO
NO
DELAY 5 BUS CYCLES
CLEAR CBEIF FLAG
FLAG SET
OR PVIOL
ACCERR
FLAG
CCIF
SET
?
?
NO
YES
PROTECTED OR
BAD COMMAND
FLASH ARRAY
COMPLETED
COMMAND
MOTOROLA
AN2153