11
P/N:PM1200
MX29F400CT/CB
REV. 0.02, APR. 15, 2005
can be tied together in parallel with a pull-up resistor to
Vcc.
If the o utput is low (Busy), the device is activ ely erasing
or programming. (This includes programming in the Erase
Suspend mo de.) If the o utput is high (Ready), the device
is ready to read array data (including during the Erase
Suspend mo de), o r is in the standby mode.
Table 4 shows the o utputs f o r R Y/BY#.
Q6:Toggle BIT I
To ggle Bit I o n Q6 indicates whether an A utomatic Pro-
gram 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 o f the final WE# o r CE#, whichever
happens first, pulse in the co mmand sequence (prio r to
the program or erase operation), and during the sector
time-out.
During an Auto matic Program o r Erase algo rithm opera-
tion, successive read cycles to any address cause Q6
to toggle. The system may use either OE# or CE# to
co ntrol the read cycles. When the o peratio n is complete,
Q6 sto ps to ggling.
After an erase co mmand sequence is written, if all sec-
tors selected f or erasing are protected, Q6 to ggles and
returns to reading arra y data. If not all selected sectors
are pro tected, the Auto matic Erase algo rithm erases the
unpro tected secto rs, and igno res the selected secto rs
that are pro tected.
The system can use Q6 and Q2 to gether to determine
whether a sector is actively erasing or is erase sus-
pended. When the device is actively erasing (that is, the
A utomatic Erase algorithm is in progress), Q6 toggling.
When the device enters the Erase Suspend mode, Q6
stops toggling. However, the system must also use Q2
to determine which sectors are erasing or erase-sus-
pended. Alternatively, the system can use Q7.
If a program address f alls within a protected sector , Q6
toggles for approximately 2 us after the program com-
mand sequence is written, then returns to reading array
data.
Q6 also toggles during the erase-suspend-program mode,
and stops toggling once the Automatic Program algorithm
is complete.
Table 4 shows the o utputs f o r To ggle Bit I o n Q6.
Q2:Toggle Bit II
The "To ggle Bit II" o n Q2, when used with Q6, indicates
whether a par ticular sector is actively erasing (that is,
the Auto matic Erase algorithm is in pro cess), or whether
that secto r is erase-suspended. Toggle Bit I is valid after
the rising edge o f the final WE# o r CE#, whiche ver hap-
pens first, pulse in the co mmand sequence .
Q2 to ggles when the system reads at addresses within
tho se sectors that have been selected fo r erasure. (The
system may use either OE# or CE# to control the read
cycles.) But Q2 cannot distinguish whether the sector
is activ ely erasing o r is erase-suspended. Q6, b y co m-
parison, indicates whether the device is actively eras-
ing, o r is in Erase Suspend, but canno t distinguish which
sectors are selected for erasure. Thus , bo th status bits
are required f o r secto rs and mo de info rmatio n. Refer to
Table 4 to co mpare o utputs f o r Q2 and Q6.
Reading Toggle Bits Q6/ Q2
Whene v er the system initially begins reading toggle bit
status, it must read Q7-Q0 at least twice in a row to
determine whether a to ggle bit is toggling. Typically , the
system would no te 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 to ggle bit is no t toggling, the device has co m-
pleted the pro gram o r erase o peratio n. The system can
read arra y data o n Q7-Q0 on the fo llowing read cycle.
How ever, if after the initial two read cycles , the system
determines that the toggle bit is still toggling, the sys-
tem also should note whether the value of Q5 is high
(see the section on Q5). If it is , the system sho uld then
determine again whether the toggle bit is toggling, since
the to ggle bit may have stopped toggling just as Q5 went
high. If the toggle bit is no longer toggling, the device
has successfully co mpleted the program o r erase o pera-
tio n. If it is still to ggling, the device did not co mplete the
operation successfully, and the system must wr ite the
reset co mmand to return to reading array data.
The remaining scenario is that system initially determines