S29AS016J datasheet(41/60 Pages) SPANSION

41 / 60 page

February 1, 2012 S29AS016J_00_11

S29AS016J

Data

She e t

12.5

Reading Toggle Bits DQ6/DQ2

Refer to Figure 12.2 on page 41 for the following discussion. Whenever the system initially begins reading

toggle bit status, it must read DQ7–DQ0 at least twice in a row to determine whether a toggle bit is toggling.

Typically, the 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 (at DQ7–DQ0 in

byte mode or DQ15–DQ0 in word mode) 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 DQ5 is high (see the section on DQ5). 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

DQ5 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 DQ5 has not

gone high. The system may continue to monitor the toggle bit and DQ5 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 12.2 on page 41).

Figure 12.2 Toggle Bit Algorithm

Notes

1. Read toggle bit twice to determine whether or not it is toggling. See text.

2. Recheck toggle bit because it may stop toggling as DQ5 changes to 1. See text.

START

Yes

DQ5 = 1?

Yes

Toggle Bit

= Toggle?

Program/Erase

Operation Not

Complete, Write

Reset Command

Program/Erase

Operation Complete

Read DQ7–DQ0

Toggle Bit

= Toggle?

Read DQ7–DQ0

Twice

Read DQ7–DQ0

(Note 1)

(Notes 1, 2)

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