AM29LV642D AMD [Advanced Micro Devices], AM29LV642D Datasheet - Page 28

• Manufacturer Part Number: AM29LV642D
• Manufacturer: AMD [Advanced Micro Devices]

See also “VersatileI/O™ (V
Bus Operations section for more information. The
Read-Only Operations table provides the read param-
eters, and Figure 13 shows the timing diagram.
Reset Command
Writing the reset command resets the device 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 se-
quence cycles in an erase command sequence before
erasing begins. This resets the device to the read
mode. Once erasure begins, however, the device ig-
nores 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. This resets the device to
the read mode. If the program command sequence is
written while the device is in the Erase Suspend mode,
writing the reset command returns the device to the
erase-suspend-read mode. Once programming be-
gins, however, the device ignores reset commands
until the operation is complete.
The reset command may be written between the se-
quence cycles in an autoselect command sequence.
Once in the autoselect mode, the reset command
must be written to return to the read mode. If the de-
vice entered the autoselect mode while in the Erase
Suspend mode, writing the reset command returns the
device to the erase-suspend-read mode.
If DQ5 goes high during a program or erase operation,
writing the reset command returns the device to the
read mode (or erase-suspend-read mode if the device
was in Erase Suspend).
Autoselect Command Sequence
The autoselect command sequence allows the host
system to access the manufacturer and device codes,
and determine whether or not a sector is protected.
Table 10 shows the address and data requirements.
This method is an alternative to that shown in Table 4,
which is intended for PROM programmers and re-
quires V
mand sequence may be written to an address that is
either in the read or erase-suspend-read mode. The
autoselect command may not be written while the de-
vice is actively programming or erasing.
The autoselect command sequence is initiated by first
writing two unlock cycles. This is followed by a third
write cycle that contains the autoselect command. The
device then enters the autoselect mode. The system
may read at any address any number of times without
initiating another autoselect command sequence:
26
ID
on address pin A9. The autoselect com-
IO
) Control” in the Device
D A T A
Am29LV642D
S H E E T
■ A read cycle at address XX00h returns the manu-
■ A read cycle at address XX01h returns the device
■ A read cycle to an address containing a sector
The system must write the reset command to return to
the read mode (or erase-suspend-read mode if the de-
vice was previously in Erase Suspend).
Word Program Command Sequence
Programming is a four-bus-cycle operation. The pro-
gram command sequence is initiated by writing two
unlock write cycles, followed by the program set-up
command. The program address and data are written
next, which in turn initiate the Embedded Program al-
gorithm. The system is not required to provide further
controls or timings. The device automatically provides
internally generated program pulses and verifies the
programmed cell margin. Table 10 shows the address
and data requirements for the word program command
sequence.
When the Embedded Program algorithm is complete,
the device then returns to the read mode and ad-
dresses are no longer latched. The system can deter-
mine the status of the program operation by using
DQ7, DQ6, or RY/BY#. Refer to the Write Operation
Status section for information on these status bits.
Any commands written to the device during the Em-
bedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program
operation. The program command sequence should
be reinitiated once the device has returned to the read
mode, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from “0” back to a “1.” Attempting to do so may
cause the device to set DQ5 = 1, or cause the DQ7
and DQ6 status bits to indicate the operation was suc-
cessful. However, a succeeding read will show that the
data is still “0.” Only erase operations can convert a “0”
to a “1.”
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram words to the device faster than using the stan-
dard program command sequence. The unlock bypass
command sequence is initiated by first writing two un-
lock cycles. This is followed by a third write cycle con-
taining the unlock bypass command, 20h. The device
then enters the unlock bypass mode. A two-cycle un-
lock bypass program command sequence is all that is
facturer code.
code.
group address (SA), and the address 02h on A7–A0
returns 01h if the sector group is protected, or 00h
if it is unprotected. (Refer to Table 5 for valid sector
addresses).
25022A2 May 5, 2006