EN29LV400A
RY/BY#: Ready/Busy Status output
The RY/BY# is a dedicated, open-drain output pin that indicates whether an Embedded Algorithm is
in progress or completed. The RY/BY# status is valid after the rising edge of the final WE# pulse in
the command sequence. Since RY/BY# is an open-drain output, several RY/BY# pins can be tied
together in parallel with a pull-up resistor to Vcc.
In the output-low period, signifying Busy, the device is actively erasing or programming. This
includes programming in the Erase Suspend mode. If the output is high, signifying the Ready, the
device is ready to read array data (including during the Erase Suspend mode), or is in the standby
mode.
DQ6: Toggle Bit I
The EN29LV400A provides a “Toggle Bit” on DQ6 to indicate the status of the embedded
programming and erase operations. (See Table 6)
During an embedded Program or Erase operation, successive attempts to read data from the device
at any address (by active OE# and CE#) will result in DQ6 toggling between “zero” and “one”. Once
the embedded Program or Erase operation is completed, DQ6 will stop toggling and valid data will
be read on the next successive attempts. During embedded Programming, the Toggle Bit is valid
after the rising edge of the fourth WE# pulse in the four-cycle sequence. During Erase operation, the
Toggle Bit is valid after the rising edge of the sixth WE# pulse for sector erase or chip erase.
In embedded Programming, if the sector being written to is protected, DQ6 will toggles for about 2
µs, then stop toggling without the data in the sector having changed. In Sector Erase or Chip Erase,
if all selected sectors are protected, DQ6 will toggle for about 100 µs. The chip will then return to the
read mode without changing data in all protected sectors.
The flowchart for the Toggle Bit (DQ6) is shown in Flowchart 6. The Toggle Bit timing diagram is
shown in Figure 9.
DQ5: Exceeded Timing Limits
DQ5 indicates whether the program or erase time has exceeded a specified internal pulse count
limit. Under these conditions DQ5 produces a “1.” This is a failure condition that indicates the
program or erase cycle was not successfully completed. Since it is possible that DQ5 can become a
1 when the device has successfully completed its operation and has returned to read mode, the user
must check again to see if the DQ6 is toggling after detecting a “1” on DQ5.
The DQ5 failure condition may appear if the system tries to program a “1” to a location that is
previously programmed to “0.” Only an erase operation can change a “0” back to a “1.” Under
this condition, the device halts the operation, and when the operation has exceeded the timing limits,
DQ5 produces a “1.” Under both these conditions, the system must issue the reset command to
return the device to reading array data.
DQ3: Sector Erase Timer
After writing a sector erase command sequence, the output on DQ3 can be used to determine
whether or not an erase operation has begun. (The sector erase timer does not apply to the chip
erase command.) When sector erase starts, DQ3 switches from “0” to “1.” This device does not
support multiple sector erase command sequences so it is not very meaningful since it immediately
shows as a “1” after the first 30h command. Future devices may support this feature.
DQ2: Erase Toggle Bit II
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
15
Rev. A, Issue Date: 2005/01/07
EON [ EON SILICON SOLUTION INC. ]
