Operation Of Dual Operation Flash - Fujitsu MB90895 Series Hardware Manual

20.3

Operation of Dual Operation Flash

Described below is the operation of Dual Operation Flash.
Pay particular attention to the following points when using Dual Operation Flash:
• Interrupt occurring when the upper bank is reprogrammed
• Sector switching register (SSR0) setting procedure
I Interrupt occurring when the upper bank is reprogrammed
Dual Operation Flash consists of two banks and, like conventional flash memory products, it
cannot execute an erase/program and a read simultaneously in the same bank.
Since SA9 contains an interrupt vector, the interrupt vector from the CPU cannot be read
normally when an interrupt occurs at write access to the upper bank. To reprogram the upper
bank, SSR0:SEN0 must be set to "1". When an interrupt occurs, therefore, SA3 is accessed to
read the interrupt vector data. The same data as SA3 and SA9 must be before setting the sector
switching register (SSR0).
I Sector switching register (SSR0) setting procedure
Figure20.3-1 illustrates the procedure of setting the sector switching register (SSR0).
The SEN0 bit must be set to "1" before reprogramming of data in the upper bank. Note also that it
is not allowed to make any change to the setting of the sector switching register (SSR0) during
write access to the flash memory. Be sure to set the sector switching register (SSR0) before or
after reprogramming the flash memory.
During setting this register, the interrupt enable is set prohibit. After setting SEN0 bit, the interrupt will be
set enable.
Figure20.3-1 The procedure of setting the sector switching register (SSR0)
FLASH data reprogramming
Start of
FLASH data writing
End of
FLASH data reprogramming
CHAPTER 20 DUAL OPERATION FLASH
Start of
Copy SA9 data to SA3
SSR0: SEN0 setting ("1")
Start of
FLASH data writing
End of
FLASH data reprogramming
SSR0: SEN0 setting ("0")
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