A29L800A Series
use either
or to control the read cycles.) But I/O2
CE
RY/
: Read/
Busy
BY
OE
cannot distinguish whether the sector is actively erasing or is
erase-suspended. I/O6, by comparison, indicates whether the
device is actively erasing, or is in Erase Suspend, but cannot
distinguish which sectors are selected for erasure. Thus, both
status bits are required for sector and mode information. Refer
to Table 6 to compare outputs for I/O2 and I/O6.
Figure 4 shows the toggle bit algorithm in flowchart form, and
the section " I/O2: Toggle Bit II" explains the algorithm. See
also the " I/O6: Toggle Bit I" subsection. Refer to the Toggle
Bit Timings figure for the toggle bit timing diagram. The I/O2
vs. I/O6 figure shows the differences between I/O2 and I/O6 in
graphical form.
The RY/
is a dedicated, open-drain output pin that indicates
BY
whether an Embedded algorithm is in progress or complete.
The RY/
status is valid after the rising edge of the final
WE
BY
pulse in the command sequence. Since RY/
is an open-
BY
drain output, several RY/
pins can be tied together in
BY
parallel with a pull-up resistor to VCC. (The RY/
available on the 44-pin SOP package)
pin is not
BY
If the output is low (Busy), the device is actively erasing or
programming. (This includes programming in the Erase
Suspend mode.) If the output is high (Ready), the device is
ready to read array data (including during the Erase Suspend
mode), or is in the standby mode.
Reading Toggle Bits I/O6, I/O2
Table 6 shows the outputs for RY/
. Refer to “
RESET
BY
Refer to Figure 4 for the following discussion. Whenever the
system initially begins reading toggle bit status, it must read
I/O7 - I/O0 at least twice in a row to determine whether a
toggle bit is toggling. Typically, a system would note and store
the value of the toggle bit after the first read. After the second
read, the system would compare the new value of the toggle
bit with the first. If the toggle bit is not toggling, the device has
completed the program or erase operation. The system can
read array data on I/O7 - I/O0 on the following read cycle.
However, if after the initial two read cycles, the system
determines that the toggle bit is still toggling, the system also
should note whether the value of I/O5 is high (see the section
on I/O5). If it is, the system should then determine again
whether the toggle bit is toggling, since the toggle bit may
have stopped toggling just as I/O5 went high. If the toggle bit is
no longer toggling, the device has successfully completed the
program or erase operation. If it is still toggling, the device did
not complete the operation successfully, and the system must
write the reset command to return to reading array data.
The remaining scenario is that the system initially determines
that the toggle bit is toggling and I/O5 has not gone high. The
system may continue to monitor the toggle bit and I/O5
through successive read cycles, determining the status as
described in the previous paragraph. Alternatively, it may
choose to perform other system tasks. In this case, the
system must start at the beginning of the algorithm when it
returns to determine the status of the operation (top of Figure
4).
Timings”, “Timing Waveforms for Program Operation” and
“Timing Waveforms for Chip/Sector Erase Operation” for more
information.
I/O6: Toggle Bit I
Toggle Bit I on I/O6 indicates whether an Embedded Program
or Erase algorithm is in progress or complete, or whether the
device has entered the Erase Suspend mode. Toggle Bit I may
be read at any address, and is valid after the rising edge of the
final
pulse in the command sequence (prior to the
WE
program or erase operation), and during the sector erase time-
out.
During an Embedded Program or Erase algorithm operation,
successive read cycles to any address cause I/O6 to toggle.
(The system may use either
or
to control the read
CE
OE
cycles.) When the operation is complete, I/O6 stops toggling.
After an erase command sequence is written, if all sectors
selected for erasing are protected, I/O6 toggles for
approximately 100µs, then returns to reading array data. If not
all selected sectors are protected, the Embedded Erase
algorithm erases the unprotected sectors, and ignores the
selected sectors that are protected.
The system can use I/O6 and I/O2 together to determine
whether a sector is actively erasing or is erase-suspended.
When the device is actively erasing (that is, the Embedded
Erase algorithm is in progress), I/O6 toggles. When the device
enters the Erase Suspend mode, I/O6 stops toggling. However,
the system must also use I/O2 to determine which sectors are
erasing or erase-suspended. Alternatively, the system can use
I/O5: Exceeded Timing Limits
I/O5 indicates whether the program or erase time has
exceeded a specified internal pulse count limit. Under these
conditions I/O5 produces a "1." This is a failure condition that
indicates the program or erase cycle was not successfully
completed.
The I/O5 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, I/O5 produces a
"1."
I/O7 (see the subsection on " I/O7 :
Polling").
Data
I/O6 also toggles during the erase-suspend-program mode, and
stops toggling once the Embedded Program algorithm is
complete.
The Write Operation Status table shows the outputs for Toggle
Bit I on I/O6. Refer to Figure 4 for the toggle bit algorithm, and
to the Toggle Bit Timings figure in the "AC Characteristics"
section for the timing diagram. The I/O2 vs. I/O6 figure shows
the differences between I/O2 and I/O6 in graphical form. See
also the subsection on " I/O2: Toggle Bit II".
Under both these conditions, the system must issue the reset
command to return the device to reading array data.
I/O2: Toggle Bit II
The "Toggle Bit II" on I/O2, when used with I/O6, indicates
whether a particular sector is actively erasing (that is, the
Embedded Erase algorithm is in progress), or whether that
sector is erase-suspended. Toggle Bit II is valid after the rising
edge of the final
I/O2 toggles when the system reads at addresses within those
pulse in the command sequence.
WE
sectors that have been selected for erasure. (The system may
(June, 2005, Version 1.1)
15
AMIC Technology, Corp.
AMICC [ AMIC TECHNOLOGY ]
