W49V002 Winbond, W49V002 Datasheet - Page 4

• Manufacturer Part Number: W49V002
• Description: 256K X 8 CMOS FLASH MEMORY WITH FWH INTERFACE
• Manufacturer: Winbond

"1" to logical data "0." The erase operation, which changed entire data in main memory and/or boot
block from "0" to "1", is needed before programming.
The program operation is initiated by a 4-byte command cycle (see Command Codes for Byte
Programming). The device will internally enter the program operation immediately after the byte-program
command is entered. The internal program timer will automatically time-out (100 S max. - T
is completed and then return to normal read mode. Data polling and/or Toggle Bits can be used to detect
end of program cycle.
Boot Block Operation and Hardware Protection at Initial- #TBL & #WP
There are two alternatives to set the boot block. One is software command sequences method; the other
is hardware method. 16K-byte in the top location of this device can be locked as boot block, which can
be used to store boot codes. It is located in the last 16K bytes of the memory with the address range
from 3C000(hex) to 3FFFF(hex).
Please see Command Codes for Boot Block Lockout Enable for the specific code. Once this feature is
set, the data for the designated block cannot be erased or programmed (programming lockout), other
memory locations can be changed by the regular programming method.
Besides the software method, there is a hardware method to protect the top boot block and other
sectors. Before program/erase to this device, set the #TBL pin to low state and then the top boot block
will not be programmed/erased. When enabling hardware top boot block, #TBL being low state, it will
override the software method setting. That is, if #TBL is at low state, then top boot block cannot be
programmed/erased no matter how the software boot block lock setting.
Another pin, #WP, will protect the whole chip if this pin is set to low state before program/erase. The
enable of this pin will override the #TBL setting. That is, the top boot block cannot be
programmed/erased if this pin is set to low no matter how the #TBL or software boot block lock setting.
Hardware Data Protection
The integrity of the data stored in the W49V002A is also hardware protected in the following ways:
(1) Noise/Glitch Protection: A #WE pulse of less than 15 nS in duration will not initiate a write cycle.
(2) V
(3) Write Inhibit Mode: Forcing #OE low or #WE high will inhibit the write operation. This prevents
(4) V
Data Polling (DQ
The W49V002A includes a data polling feature to indicate the end of a program or erase cycle. When
the W49V002A is in the internal program or erase cycle, any attempts to read DQ
loaded will receive the complement of the true data. Once the program or erase cycle is completed, DQ
will show the true data. Note that DQ
has been completed it becomes logical "1" or true data.
Toggle Bit (DQ
In addition to data polling, the W49V002A provides another method for determining the end of a program
cycle. During the internal program or erase cycle, any consecutive attempts to read DQ
alternating 0's and 1's. When the program or erase cycle is completed, this toggling between 0's and 1's
will stop. The device is then ready for the next operation.
typical.
inadvertent writes during power-up or power-down periods.
mS before any write (erase/program) operation.
DD
DD
Power Up/Down Detection: The programming operation is inhibited when V
power-on delay: When V
6
)- Write Status Detection
7
)- Write Status Detection
DD
has reached its sense level, the device will automatically time-out 5
7
will show logical "0" during the erase cycle, and when erase cycle
- 4 -
Preliminary W49V002A
DD
7
is less than 1.5V
of the last byte
6
will produce
BP
) once it
7