参数资料
型号: AM29LV004B-90REC
厂商: ADVANCED MICRO DEVICES INC
元件分类: PROM
英文描述: 4 Megabit (512 K x 8-Bit) CMOS 3.0 Volt-only Boot Sector Flash Memory
中文描述: 512K X 8 FLASH 3V PROM, 90 ns, PDSO40
封装: TSOP-40
文件页数: 18/36页
文件大小: 455K
代理商: AM29LV004B-90REC
18
Am29LV004
P R E L I M I N A R Y
The remaining scenario is that the system initially de-
termines 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, de-
termining the status as described in the previous para-
graph. 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).
DQ5: Exceeded Timing Limits
DQ5 indicates whether the program or erase time has
exceeded a specified internal pulse count limit. Under
these conditions DQ5 produces a “1.” This is a failure
condition that indicates the program or erase cycle was
not successfully completed.
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 additional
sectors are selected for erasure, the entire time-out also
applies after each additional sector erase command.
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
μ
s. 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# Poll-
ing) or DQ6 (Toggle Bit I) to ensure the device has ac-
cepted the command sequence, and then read DQ3. If
DQ3 is “1”, the internally controlled erase cycle has be-
gun; all further commands (other than Erase Suspend)
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 ac-
cepted. Table 6 shows the outputs for DQ3.
START
No
Yes
Yes
DQ5 = 1
No
Yes
Toggle Bit
= Toggle
No
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
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.
21522A-7
Figure 5.
Toggle Bit Algorithm
(Notes
1, 2)
(Note 1)
相关PDF资料
PDF描述
Am29LV004T-90RFEB 4 Megabit (512 K x 8-Bit) CMOS 3.0 Volt-only Boot Sector Flash Memory
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