Infineon Cypress S29GL01GS, Manual

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Document Number: 001-98285 Rev. *R Page 37 of 108
S29GL01GS/S29GL512S
S29GL256S/S29GL128S
5.5.2.4 DQ2: Toggle Bit II
Toggle Bit II on DQ2, when used with DQ6, 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.
DQ2 toggles when the system reads at addresses within the sector selected for erasure. (The system may use either OE# or CE# to
control the read cycles). But DQ2 cannot distinguish whether the sector is actively erasing or is erase-suspended. DQ6, by
comparison, indicates whether the device is actively erasing, or is in Erase Suspend, but cannot distinguish if the sector is selected
for erasure. Thus, both status bits are required for sector and mode information. Refer to
Table 5.3 on page 39 to compare outputs
for DQ2 and DQ6. Figure 5.5 on page 36 shows the toggle bit algorithm in flowchart form, and the Reading Toggle Bits DQ6/DQ2
on page 37 explains the algorithm. See also Figure 5.6 on page 37 shows the toggle bit timing diagram. Figure 5.2 on page 25
shows the differences between DQ2 and DQ6 in graphical form.
5.5.2.5 Reading Toggle Bits DQ6/DQ2
Refer to Figure 5.5 on page 36 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
previous value. If the toggle bit is not toggling, the device has completed the program or erases operation. The system can read
array data on DQ15-DQ0 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
DQ5: Exceeded Timing Limits on page 38 ). 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 5.6 on page 37 ).
Figure 5.6 Toggle Bit Program
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
Read DQ7 -DQ0 (Note 1)
Erase/Program
Operation Not
Complete
Toggle Bit
= Toggle?
Yes
No
DQ5 = 1?
No
Yes
Read DQ7 -DQ0 Twice (Notes 1, 2)
Toggle Bit
= Toggle?
Yes
No
Erase/Program
Operation Complete
Read DQ7 -DQ0