This detailed information is for your reference. It may
prove easier to always issue the Reset command two
consecutive times. This eliminates the need to deter-
mine if you are in the Setup Program state or not.
in-system, manufacturer and device codes must be
accessible while the device resides in the target
system. PROM programmers typically access the sig-
nature codes by raising A9 to a high voltage. However,
multiplexing high voltage onto address lines is not a
generally desired system design practice.
In-System Programming Considerations
Flash memories can be programmed in-system or in a
standard PROM programmer. The device may be sol-
dered to the circuit board upon receipt of shipment and
programmed in-system. Alternatively, the device may
initially be programmed in a PROM programmer prior
to soldering the device to the circuit board.
The device contains an Auto Select operation to supple-
ment traditional PROM programming methodologies.
The operation is initiated by writing 80h or 90h into the
command register. Following this command, a read
cycle address 0000h retrieves the manufacturer code of
01h (AMD). A read cycle from address 0001h returns
the device code (see the Auto Select Code table of the
corresponding device data sheet). To terminate the op-
eration, it is necessary to write another valid command,
such as Reset (00h or FFh), into the register.
Auto Select Command
AMD’s Flash memories are designed for use in appli-
cations where the local CPU alters memory contents.
In order to correctly program any Flash memories
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Am28F256A
SPANSION [ SPANSION ]
