
October 10, 2006  21521D6
Am29LV200B
21
D AT A  S H E E T
RY/BY#: Ready/Busy#
The RY/BY# is a dedicated, open-drain output pin that 
indicates whether an Embedded Algorithm is in 
progress or complete. The RY/BY# status is valid after 
the rising edge of the final WE# pulse in the command 
sequence. Since RY/BY# is an open-drain output, 
several RY/BY# pins can be tied together in parallel 
with a pull-up resistor to V
CC
.
If the output is low (Busy), the device is actively erasing 
or programming. (This includes programming in the 
Erase Suspend mode.) If the output is high (Ready), 
the device is ready to read array data (including during 
the Erase Suspend mode), or is in the standby mode.
Table 6 shows the outputs for RY/BY#. Figures 14, 17 
and 18 shows RY/BY# for reset, program, and erase 
operations, respectively.
DQ6: Toggle Bit I
Toggle Bit I on DQ6 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 DQ6 to toggle. The system may use either OE# 
or CE# to control the read cycles. When the operation 
is complete, DQ6 stops toggling.
After an erase command sequence is written, if all 
sectors selected for erasing are protected, DQ6 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 DQ6 and DQ2 together to deter-
mine 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), DQ6 
toggles. When the device enters the Erase Suspend 
mode, DQ6 stops toggling. However, the system must 
also use DQ2 to determine which sectors are erasing 
or erase-suspended. Alternatively, the system can use 
DQ7 (see the subsection on DQ7: Data# Polling).
If a program address falls within a protected sector, 
DQ6 toggles for approximately 1 μs after the program 
command sequence is written, then returns to reading 
array data.
DQ6 also toggles during the erase-suspend-program 
mode, and stops toggling once the Embedded 
Program algorithm is complete.
Table 6 shows the outputs for Toggle Bit I on DQ6. 
Figure 6 shows the toggle bit algorithm. Figure 20 in the 
“AC Characteristics” section shows the toggle bit timing 
diagrams. Figure 21 shows the differences between 
DQ2 and DQ6 in graphical form. See also the subsec-
tion on DQ2: Toggle Bit II.
DQ2: Toggle Bit II
The “Toggle Bit II” on DQ2, when used with DQ6, indi-
cates 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 those sectors that have been selected for era-
sure. (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-sus-
pended. DQ6, by comparison, indicates whether the 
device is actively erasing, or is in Erase Suspend, but 
cannot distinguish which sectors are selected for era-
sure. Thus, both status bits are required for sector and 
mode information. Refer to Table 6 to compare outputs 
for DQ2 and DQ6. 
Figure 6 shows the toggle bit algorithm in flowchart 
form, and the section “DQ2: Toggle Bit II” explains the 
algorithm. See also the DQ6: Toggle Bit I subsection. 
Figure 20 shows the toggle bit timing diagram. Figure 
21 shows the differences between DQ2 and DQ6 in 
graphical form. 
Reading Toggle Bits DQ6/DQ2
Refer to Figure 6 for the following discussion. When-
ever 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 com-
pleted the program or erase operation. The system can 
read array data on DQ7–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 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 tog-
gling 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 completed the operation successfully, 
and the system must write the reset command to return 
to reading array data.