MX29F400C T/B
RY/BY#:Ready/Busy#
The RY/BY# is a dedicated, open-drain output pin that
indicates whether an Automatic Erase/Program algorithm
is in progress or complete. The RY/BY# status is valid
after the rising edge of the final WE# or CE#, whichever
happens first, 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
Vcc.
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 4 shows the outputs for RY/BY#.
pended. Alternatively, the system can use Q7.
If a program address falls 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 outputs for Toggle Bit I on Q6.
Q2:Toggle Bit II
The "Toggle Bit II" on Q2, when used with Q6, indicates
whether a particular sector is actively erasing (that is,
the Automatic Erase algorithm is in process), or whether
that sector is erase-suspended. Toggle Bit I is valid after
the rising edge of the final WE# or CE#, whichever hap-
pens first, pulse in the command sequence.
Q2 toggles when the system reads at addresses within
those sectors that have been selected for erasure. (The
system may use either OE# or CE# to control the read
cycles.) But Q2 cannot distinguish whether the sector
is actively erasing or is erase-suspended. Q6, by com-
parison, indicates whether the device is actively eras-
ing, or is in Erase Suspend, but cannot distinguish which
sectors are selected for erasure. Thus, both status bits
are required for sectors and mode information. Refer to
Table 4 to compare outputs for Q2 and Q6.
Q6:Toggle BIT I
Toggle Bit I on Q6 indicates whether an Automatic 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 of the final WE# or CE#, whichever
happens first, pulse in the command sequence (prior to
the program or erase operation), and during the sector
time-out.
During an Automatic Program or Erase algorithm opera-
tion, successive read cycles to any address cause Q6
to toggle. The system may use either OE# or CE# to
control the read cycles. When the operation is complete,
Q6 stops toggling.
After an erase command sequence is written, if all sec-
tors selected for erasing are protected, Q6 toggles and
returns to reading array data. If not all selected sectors
are protected, the Automatic Erase algorithm erases the
unprotected sectors, and ignores the selected sectors
that are protected.
The system can use Q6 and Q2 together to determine
whether a sector is actively erasing or is erase sus-
pended. When the device is actively erasing (that is, the
Automatic 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-
Reading Toggle Bits Q6/ Q2
Whenever the system initially begins reading toggle bit
status, it must read Q7-Q0 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 Q7-Q0 on the following read cycle.
However, 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 should then
P/N:PM1200
REV. 1.0, DEC. 20, 2005
11
MCNIX [ MACRONIX INTERNATIONAL ]
