AM29F002BB-70EE データシートの表示（PDF） - Advanced Micro Devices

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AM29F002BB-70EE

2 Megabit (256 K x 8-Bit) CMOS 5.0 Volt-only Boot Sector Flash Memory

Advanced Micro Devices 

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

system may read DQ3 to determine whether or not an

erase operation has begun. (The sector erase timer

does not apply to the chip erase command.) If addi-

tional sectors are selected for erasure, the entire time-

out also applies after each additional sector erase com-

mand. When the time-out is complete, DQ3 switches

from “0” to “1.” The system may ignore DQ3 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 DQ7 (Data#

Polling) or DQ6 (Toggle Bit I) to ensure the device has

accepted the command sequence, and then read DQ3.

If DQ3 is “1”, the internally controlled erase cycle has

begun; all further commands (other than Erase Sus-

pend) are ignored until the erase operation is complete.

If DQ3 is “0”, the device will accept additional sector

erase commands. To ensure the command has been

accepted, the system software should check the status

of DQ3 prior to and following each subsequent sector

erase command. If DQ3 is high on the second status

check, the last command might not have been

accepted. Table 6 shows the outputs for DQ3.

START

Read DQ7–DQ0

Read DQ7–DQ0 (Note 1)

Toggle Bit

No

= Toggle?

Yes

No

DQ5 = 1?

Yes

Read DQ7–DQ0 (Notes

Twice

1, 2)

Toggle Bit

No

= Toggle?

Yes

Program/Erase

Operation Not

Complete, Write

Reset Command

Program/Erase

Operation Complete

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.

Figure 5. Toggle Bit Algorithm

November 28, 2000

Am29F002B/Am29F002NB

19

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