28F004/400B3, 28F008/800B3, 28F016/160B3, 28F320B3, 28F640B3
To read the manufacturer and device codes, the device must be in read identifier mode, which can
be reached by writing the Read Identifier command (90H). Once in read identifier mode, A0 = 0
outputs the manufacturer’s identification code and A0 = 1 outputs the device identifier (see
Table 5) Note: A1–A21 = 0. To return to read array mode, write the Read Array command (FFH).
Table 5. Read Identifier Table
Read Status Register
The device status register indicates when a program or erase operation is complete and the success
or failure of that operation. To read the status register issue the Read Status Register (70H)
command to the CUI. This causes all subsequent read operations to output data from the status
register until another command is written to the CUI. To return to reading from the array, issue the
Read Array (FFH) command.
The status register bits are output on DQ0–DQ7. The upper byte, DQ8–DQ15, outputs 00H during a
Read Status Register command.
The contents of the status register are latched on the falling edge of OE# or CE#. This prevents
possible bus errors which might occur if status register contents change while being read. CE# or
OE# must be toggled with each subsequent status read, or the status register will not indicate
completion of a program or erase operation.
When the WSM is active, SR.7 will indicate the status of the WSM; the remaining bits in the status
register indicate whether or not the WSM was successful in performing the desired operation (see
Table 7 on page 14).
Clearing the Status Register
The WSM sets status bits 1 through 7 to “1,” and clears bits 2, 6 and 7 to “0,” but cannot clear
status bits 1 or 3 through 5 to “0.” Because bits 1, 3, 4 and 5 indicate various error conditions, these
bits can only be cleared through the Clear Status Register (50H) command. By allowing the system
software to control the resetting of these bits, several operations may be performed (such as
cumulatively programming several addresses or erasing multiple blocks in sequence) before