Rainbow Electronics AT29LV040A - Manual (Page 3)

3
AT29LV040A
0334F–FLASH–05/02
The 256 bytes of data must be loaded into each sector. Any byte that is not loaded during the
programming of its sector will be erased to read FFH. Once the bytes of a sector are loaded
into the device, they are simultaneously programmed during the internal programming period.
After the first data byte has been loaded into the device, successive bytes are entered in the
same manner. Each new byte to be programmed must have its high-to-low transition on WE
(or CE) within 150 µs of the low-to-high transition of WE (or CE) of the preceding byte. If a
high-to-low transition is not detected within 150 µs of the last low-to-high transition, the load
period will end and the internal programming period will start. A8 to A18 specify the sector
address. The sector address must be valid during each high-to-low transition of WE (or CE).
A0 to A7 specify the byte address within the sector. The bytes may be loaded in any order;
sequential loading is not required. Once a programming operation has been initiated, and for
the duration of t
WC
, a read operation will effectively be a polling operation.
HARDWARE DATA PROTECTION: Hardware features protect against inadvertent pro-
grams to the AT29LV040A in the following ways: (a) V
CC
sense – if V
CC
is below 1.8V (typical),
the program function is inhibited; (b) V
CC
power on delay – once V
CC
has reached the V
CC
sense level, the device will automatically time out 10 ms (typical) before programming; (c) Pro-
gram inhibit – holding any one of OE low, CE high or WE high inhibits program cycles; and
(d) Noise filter – pulses of less than 15 ns (typical) on the WE or CE inputs will not initiate a
program cycle.
INPUT LEVELS: While operating with a 3.3V ±10% power supply, the address inputs and
control inputs (OE, CE and WE) may be driven from 0 to 5.5V without adversely affecting the
operation of the device. The I/O lines can only be driven from 0 to 3.6V.
PRODUCT IDENTIFICATION: The product identification mode identifies the device and
manufacturer as Atmel. It may be accessed by hardware or software operation. The hardware
operation mode can be used by an external programmer to identify the correct programming
algorithm for the Atmel product. In addition, users may wish to use the software product identi-
fication mode to identify the part (i.e., using the device code), and have the system software
use the appropriate sector size for program operations. In this manner, the user can have a
common board design for 256K to 4-megabit densities and, with each density’s sector size in
a memory map, have the system software apply the appropriate sector size.
For details, see Operating Modes (for hardware operation) or Software Product Identification.
The manufacturer and device code is the same for both modes.
DATA POLLING: The AT29LV040A features DATA polling to indicate the end of a program
cycle. During a program cycle an attempted read of the last byte loaded will result in the com-
plement of the loaded data on I/O7. Once the program cycle has been completed, true data is
valid on all outputs and the next cycle may begin. DATA polling may begin at any time during
the program cycle.
TOGGLE BIT: In addition to DATA polling the AT29LV040A provides another method for
determining the end of a program or erase cycle. During a program or erase operation, suc-
cessive attempts to read data from the device will result in I/O6 toggling between one and
zero. Once the program cycle has completed, I/O6 will stop toggling and valid data will be
read. Examining the toggle bit may begin at any time during a program cycle.
OPTIONAL CHIP ERASE MODE: The entire device can be erased by using a 6-byte soft-
ware code. Please see Software Chip Erase application note for details.
BOOT BLOCK PROGRAMMING LOCKOUT: The AT29LV040A has two designated mem-
ory blocks that have a programming lockout feature. This feature prevents programming of
data in the designated block once the feature has been enabled. Each of these blocks con-
sists of 16K bytes; the programming lockout feature can be set independently for either block.
While the lockout feature does not have to be activated, it can be activated for either or both
blocks.