EN29LV400A
To access the autoselect codes in-system; the host system can issue the autoselect command via
the command register, as shown in the Command Definitions table. This method does not require
VID. See “Command Definitions” for details on using the autoselect mode.
Write Mode
Write operations, including programming data and erasing sectors of memory, require the host
system to write a command or command sequence to the device. Write cycles are initiated by
placing the byte or word address on the device’s address inputs while the data to be written is input
on DQ[7:0] in Byte Mode (BYTE# = L) or on DQ[15:0] in Word Mode (BYTE# = H). The host system
must drive the CE# and WE# pins Low and the OE# pin high for a valid write operation to take place.
All addresses are latched on the falling edge of WE# and CE#, whichever happens later. All data is
latched on the rising edge of WE# or CE#, whichever happens first. The system is not required to
provide further controls or timings. The device automatically provides internally generated program /
erase pulses and verifies the programmed /erased cells’ margin. The host system can detect
completion of a program or erase operation by observing the RY/BY# pin, or by reading the DQ[7]
(Data# Polling) and DQ[6] (Toggle) status bits.
The ‘Command Definitions’ section of this document provides details on the specific device
commands implemented in the EN29LV400A.
Sector Protection/Unprotection
The hardware sector protection feature disables both program and erase operations in any sector. The
hardware sector unprotection feature re-enables both program and erase operations in previously
protected sectors.
There are two methods to enabling this hardware protection circuitry. The first one requires only
that the RESET# pin be at VID and then standard microprocessor timings can be used to enable or
disable this feature. See Flowchart 7a and 7b for the algorithm and Figure 12 for the timings.
When doing Sector Unprotect, all the other sectors should be protected first.
The second method is meant for programming equipment. This method requires VID be applied to
both OE# and A9 pin and non-standard microprocessor timings are used. This method is described
in a separate document called EN29LV400A Supplement, which can be obtained by contacting a
representative of Eon Silicon Devices, Inc.
Temporary Sector Unprotect
Start
This feature allows temporary unprotection of previously protected
sector groups to change data while in-system. The Sector
Unprotect mode is activated by setting the RESET# pin to VID.
During this mode, formerly protected sectors can be programmed
or erased by simply selecting the sector addresses. Once is
removed from the RESET# pin, all the previously protected sectors
Reset#=VID (note 1)
Perform Erase or Program
Operations
are protected again.
diagrams for more details.
See accompanying figure and timing
Reset#=VIH
Notes:
Temporary Sector
Unprotect Completed (note 2)
1. All protected sectors unprotected.
2. Previously protected sectors protected
again.
This Data Sheet may be revised by subsequent versions
or modifications due to changes in technical specifications.
©2005 Eon Silicon Solution, Inc., www.essi.com.tw
9
Rev. A, Issue Date: 2005/01/07
EON [ EON SILICON SOLUTION INC. ]
