AM29BDS640G datasheet(33/77 Pages) AMD

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May 9, 2006 25903C2

Am29BDS640G

Data

Sheet

Reset Command

Writing the reset command resets the banks to the read or erase-suspend-read

mode. Address bits are don’t cares for this command.

The reset command may be written between the sequence cycles in an erase

command sequence before erasing begins. This resets the bank to which the sys-

tem was writing to the read mode. Once erasure begins, however, the device

ignores reset commands until the operation is complete.

The reset command may be written between the sequence cycles in a program

command sequence before programming begins (prior to the third cycle). This re-

sets the bank to which the system was writing to the read mode. If the program

command sequence is written to a bank that is in the Erase Suspend mode, writ-

ing the reset command returns that bank to the erase-suspend-read mode. Once

programming begins, however, the device ignores reset commands until the op-

eration is complete.

The reset command may be written between the sequence cycles in an autoselect

command sequence. Once in the autoselect mode, the reset command must be

written to return to the read mode. If a bank entered the autoselect mode while

in the Erase Suspend mode, writing the reset command returns that bank to the

erase-suspend-read mode.

If DQ5 goes high during a program or erase operation, writing the reset command

returns the banks to the read mode (or erase-suspend-read mode if that bank

was in Erase Suspend).

The reset command is used to exit the sector lock/unlock sequence. This com-

mand is required before reading from the bank selected for sector lock/unlock

operations.

Autoselect Command Sequence

The autoselect command sequence allows the host system to access the manu-

facturer and device codes, and determine whether or not a sector is protected.

Table 13, “Command Definitions,” on page 37 shows the address and data re-

quirements. The autoselect command sequence may be written to an address

within a bank that is either in the read or erase-suspend-read mode. The autose-

lect command may not be written while the device is actively programming or

erasing in the other bank.

The autoselect command sequence is initiated by first writing two unlock cycles.

This is followed by a third write cycle that contains the bank address and the au-

toselect command. The bank then enters the autoselect mode. No subsequent

data will be made available if the autoselect data is read in synchronous mode.

The system may read at any address within the same bank any number of times

without initiating another autoselect command sequence. The following table de-

scribes the address requirements for the various autoselect functions, and the

resulting data. BA represents the bank address, and SA represents the sector ad-

dress. The device ID is read in three cycles.

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