A29L040AL datasheet(13/30 Pages) AMICC

13 / 30 page

A29L040A Series

PRELIMINARY (March, 2005, Version 0.0)

AMIC Technology, Corp.

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

WE pulse in the command sequence (prior to the

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

OE or CE to control the read

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 100

µs, 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/O7 (see the subsection on " I/O7 :

Data

Polling").

If a program address falls within a protected sector, I/O6

toggles for approximately 2

µs after the program command

sequence is written, then returns to reading array 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".

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

WE pulse in the command sequence.

I/O2 toggles when the system reads at addresses within those

sectors that have been selected for erasure. (The system may

use either

OE or CE to control the read cycles.) But I/O2

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 5 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.

Reading Toggle Bits I/O6, I/O2

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).

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."

Under both these conditions, the system must issue the reset

command to return the device to reading array data.

I/O3: Sector Erase Timer

After writing a sector erase command sequence, the system

may read I/O3 to determine whether or not an erase

operation has begun. (The sector erase timer does not apply

to the chip erase command.) If additional sectors are

selected for erasure, the entire time-out also applies after

each additional sector erase command. When the time-out is

complete, I/O3 switches from "0" to "1." The system may

ignore I/O3 if the system can guarantee that the time

between additional sector erase commands will always be

less than 50

µs. See also the "Sector Erase Command

Sequence" section.

After the sector erase command sequence is written, the

system should read the status on I/O7 (

Data Polling) or I/O6

(Toggle Bit 1) to ensure the device has accepted the

command sequence, and then read I/O3. If I/O3 is "1", the

internally controlled erase cycle has begun; all further

commands (other than Erase Suspend) are ignored until the

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