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March 12, 2004
Am49DL3208G
11
ADV ANCE
I N FO RMAT I O N
ensures that no spurious alteration of the memory
content occurs during the power transition. No com-
mand is necessary in this mode to obtain array data.
Standard microprocessor read cycles that assert valid
addresses on the device address inputs produce valid
data on the device data outputs. Each bank remains
enabled for read access until the command register
contents are altered.
specifications and to
Figure 16 for the timing diagram.
I
CC1 in the DC Characteristics table represents the ac-
tive current specification for reading array data.
Writing Commands/Command Sequences
To write a command or command sequence (which in-
cludes programming data to the device and erasing
sectors of memory), the system must drive WE# and
CE#f to V
IL, and OE# to VIH.
The device features an Unlock Bypass mode to facili-
tate faster programming. Once a bank enters the Un-
lock Bypass mode, only two write cycles are required
to program a word or byte, instead of four. The “Pro-
gram Command Sequence” section has details on
programming data to the device using both standard
and Unlock Bypass command sequences.
An erase operation can erase one sector, multiple sec-
tors, or the entire device. Tables
2 and
4 indicate the
address space that each sector occupies. Similarly, a
“sector address” is the address bits required to
tions” section has details on erasing a sector or the
entire chip, or suspending/resuming the erase opera-
tion.
The device address space is divided into four banks. A
“bank address” is the address bits required to uniquely
select a bank.
I
CC2 in the DC Characteristics table represents the ac-
tive current specification for the write mode. The
Flashtion tables and timing diagrams for write operations.
Accelerated Program Operation
The device offers accelerated program operations
through the ACC function. This is one of two functions
provided by the WP#/ACC pin. This function is prima-
rily intended to allow faster manufacturing throughput
at the factory.
If the system asserts V
HH on this pin, the device auto-
matically enters the aforementioned Unlock Bypass
mode, temporarily unprotects any protected sectors,
and uses the higher voltage on the pin to reduce the
time required for program operations. The system
would use a two-cycle program command sequence
as required by the Unlock Bypass mode. Removing
V
HH from the WP#/ACC pin returns the device to nor-
mal operation. Note that V
HH must not be asserted on
WP#/ACC for operations other than accelerated pro-
gramming, or device damage may result. In addition,
the WP#/ACC pin must not be left floating or uncon-
nected; inconsistent behavior of the device may result.
mation.
Autoselect Functions
If the system writes the autoselect command se-
quence, the device enters the autoselect mode. The
system can then read autoselect codes from the inter-
nal register (which is separate from the memory array)
on DQ15–DQ0. Standard read cycle timings apply in
quence sections for more information.
Simultaneous Read/Write Operations with
Zero Latency
This device is capable of reading data from one bank
of memory while programming or erasing in the other
bank of memory. An erase operation may also be sus-
pended to read from or program to another location
within the same b ank (except the sector bein g
erased).
Figure 21 shows how read and write cycles
may be initiated for simultaneous operation with zero
latency. I
CC6f and ICC7f in the table represent the cur-
rent specifications for read-wh ile -pro gram an d
read-while-erase, respectively.
Standby Mode
When the system is not reading or writing to the de-
vice, it can place the device in the standby mode. In
this mode, current consumption is greatly reduced,
and the outputs are placed in the high impedance
state, independent of the OE# input.
The device enters the CMOS standby mode when the
CE#f and RESET# pins are both held at V
CC ± 0.3 V.
(Note that this is a more restricted voltage range than
V
IH.) If CE#f and RESET# are held at VIH, but not
within V
CC ± 0.3 V, the device will be in the standby
mode, but the standby current will be greater. The de-
vice requires standard access time (t
CE) for read ac-
cess when the device is in either of these standby
modes, before it is ready to read data.
If the device is deselected during erasure or program-
ming, the device draws active curren t until the
operation is completed.
I
CC3f in the table represents the standby current spec-
ification.