Data Writing - Fujitsu MB91319 Series Hardware Manual

19.6.2

Data Writing

This section explains how to issue a Write command to write data to flash memory.
■ Data Writing
The automatic data write algorithm can be started by continuously sending write commands
(listed in the command sequence table) to target sectors in flash memory. The automatic
algorithm and automatic writing start when writing data to the target address terminates in the
fourth cycle.
❍ How to specify address
Only even-numbered addresses can be specified in write data cycles. If an odd-numbered
address is specified, data cannot be written correctly. In other words, data must be written to
even-numbered addresses in units of half-words.
Data can be written by freely specifying the order of addresses where data is to be written.
Moreover, data can be written beyond sector boundaries. Note that items of data can only be
written with each write command in units of half-words.
❍ Notes on writing data
Data "0" cannot be changed to "1" in a write operation. If data "1" is overwritten, the data polling
algorithm or toggle operation does not terminate, and the flash memory device is considered
defective. An error is assumed with the time limit over flag if the specified write time is exceeded,
or if only data "1" is apparently written, although data "0" is read in read/reset status. Data "0" can
be changed to "1" only with an erase operation. All commands are ignored during automatic
writing. If a hardware reset is activated during writing, the data being written is not guaranteed.
❍ Write procedure
Figure 19.6-1 shows an example of the write procedure.
The status of the automatic algorithm in flash memory can be checked using the hardware
sequence flag. In the example in Figure 19.6-1, the data polling flag (DPOLL) is used to check for
termination of the write operation.
Data for the flag check is read from the address where the last data was written.
The data polling flag (DPOLL) changes together with the time limit over flag (TLOVER).
Therefore, DPOLL must be rechecked even though TLOVER is set to "1."
The toggle bit flag (TOGGLE) also stops toggling simultaneously when the value of TLOVER is
changed to "1." Therefore, this flag must also be rechecked.
CHAPTER 19 FLASH MEMORY
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