Filter
Top Products
1000
Chapter 54 Flash Memory
7.Auto Algorithms
7.2 Auto Algorithm Commands
■ Read/reset command
Issue a Read/reset command sequence to recover to read mode after a timing limit has been exceeded. Data
is read from Flash memory via the read cycle. Flash memory stays in a read state until another command is
input.
When powered up, Flash memory is automatically set to read/reset. In this case, commands are not required
for data reading.
■ Program (write)
In CPU programming mode, writes are performed in basic units of half words. Writes are performed in 4 bus
operations. The command sequence as two “unlock” cycles, followed by a write setup command and write
data cycle. Then, in the final write cycle, writing to memory starts.
After the auto write algorithm command sequence is executed, Flash memory no longer requires external
control. Flash memory generates appropriate write pulses that it has automatically created internally, and
validates the margins of written cells. Auto write operation ends when the bit 7 data matches the data written
to this bit via data polling (see (3) Hardware sequence flag). Flash memory then returns to read mode, and no
longer accepts write addresses. As a result, at this time Flash memory requests the next valid address. Thus,
data polling indicates that writing is ongoing.
During writing, all commands written to Flash memory are ignored. If a hardware reset is started during writing,
the data in addresses that have been written is not guaranteed. Data can be written to addresses in any order,
and may also cross sector boundaries. Writing cannot return data “0” to data “1”. If data “1” is written to data
“0”, then either the data polling algorithm will determine that the device is bad, or it will appear that data “1”
has been written, but in reset/read mode, when the data is read, it will still be read as “0”. Only erase operation
can change “0” data to “1” data.
Figure 7-1 The Writing Sequence Using Write Commands
Start write
Write command sequence
Device data polling
Last address?
Write finished
Next address
No
YES