Operation Of Dual Operation Flash Memory - Fujitsu MB90335 Series Hardware Manual

CHAPTER 22 DUAL OPERATION FLASH MEMORY

22.8 Operation of Dual Operation Flash Memory

22.8 Operation of Dual Operation Flash Memory
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
■ 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).
■ Sector Switching Register (SSR0) Setting Procedure
Figure 22.8-1 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.
Figure 22.8-1 The Procedure of Setting the Sector Switching Register (SSR0)
FLASH data reprogramming
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FLASH data reprogramming
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FLASH data writing
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FUJITSU MICROELECTRONICS LIMITED
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Copy SA9 data to SA3
SSR0: SEN0 setting ("1")
FLASH data writing
FLASH data reprogramming
SSR0: SEN0 setting ("0")
MB90335 Series
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CM44-10137-6E