w49f201 Winbond Electronics Corp America, w49f201 Datasheet - Page 3

• Manufacturer Part Number: w49f201
• Description: 128k X 16 Cmos Flash Memory
• Manufacturer: Winbond Electronics Corp America

Preliminary W49F201
FUNCTIONAL DESCRIPTION
Read Mode
The read operation of the W49F201 is controlled by CE and OE, both of which have to be low for
the host to obtain data from the outputs. CE is used for device selection. When CE is high, the chip
is de-selected and only standby power will be consumed. OE is the output control and is used to gate
data to the output pins. The data bus is in high impedance state when either CE or OE is high. Refer
to the timing waveforms for further details.
Reset Operation
The RESET input pin can be used in some application. When RESET pin is at high state, the device
is in normal operation mode. When RESET pin is driven low for at least a period of T
, it will halts
RP
the device and all outputs are at high impedance state. The device also resets the internal state
machine to read array data. The operation that was interrupted should be reinitiated once the device
is ready to accept another command sequence to assure data integrity. As the high state re-asserted
to the RESET pin, the device will return to read or standby mode, it depends on the control signals.
The system can read data T
after the RESET pin returns to V
. The other function for RESET pin
IH
RH
is temporary reset the boot block. By applying the 12V to RESET pin, the boot block can be
reprogrammed even though the boot block lockout function is enabled.
Boot Block Operation
There is one 8K-word boot block in this device, which can be used to store boot code. It is located in
the first 8K words of the memory with the address range from 0000(hex) to 1FFF(hex).
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.
There is one condition that the lockout feature can be overrides. Just apply 12V to RESET pin, the
lockout feature will temporary be inactivated and the boot block can be erased/programmed. Once
the RESET pin returns to TTL level, the lockout feature will be activated again.
In order to detect whether the boot block feature is set on the 8K-words block, users can perform
software command sequence: enter the product identification mode (see Command Codes for
Identification/Boot Block Lockout Detection for specific code), and then read from address "0002
hex". If the output data in DQ0 is "1", the boot block programming lockout feature is activated; if the
output data in DQ0 is "0",
the lockout feature is inactivated and the block can be
erased/programmed.
To return to normal operation, perform a three-byte command sequence (or an alternate single-word
command) to exit the identification mode. For the specific code, see Command Codes for
Identification/Boot Block Lockout Detection.
Chip Erase Operation
The chip-erase mode can be initiated by a six-word command sequence. After the command loading
cycle, the device enters the internal chip erase mode, which is automatically timed and will be
Publication Release Date: June 1999
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Revision A1