11
P/N:PM1081 REV. 1.5, FEB. 26, 2008
MX29LV640BU
WRITE COMMANDS/COMMAND SEQUENCES
To write a co mmand to the de vice, system m ust drive WE# and CE# to Vil, and OE# to Vih. In a command cycle, all
address are latched at the later falling edge of CE# and WE#, and all data are latched at the earlier rising edge of CE#
and WE#.
Figure 1 illustrates the A C timing wavefo rm of a write co mmand, and Table 3 defines all the valid command sets o f the
device. System is not allowed to write invalid commands no t defined in this datasheet. Writing an invalid command will
bring the device to an undefined state.
REQUIREMENTS FOR READING ARRAY DA T A
Read array actio n is to read the data stored in the array . While the memo ry device is in powered up o r has been reset,
it will auto matically enter the status of read array. If the micropro cessor wants to read the data sto red in the arra y , it has
to drive CE# (device enab le co ntrol pin) and OE# (Output co ntro l pin) as Vil, and input the address o f the data to be
read into address pin at the same time. After a per iod of read cycle (Tce or Taa), the data being read out will be
displayed o n output pin fo r micro processor to access. If CE# or OE# is Vih, the output will be in tri-state, and there will
be no data displa yed on output pin at all.
After the memo ry device co mpletes embedded o peratio n (automatic Erase o r Pro gram), it will auto matically return to
the status o f read arra y, and the device can read the data in any address in the arra y. In the pro cess o f erasing, if the
de vice receiv es the Er ase suspend command, erase o peration will be stopped tempo r arily after a perio d of time no
mo re than Tready and the device will return to the status o f read array. At this time, the device can read the data stored
in any address e xcept the sector being erased in the arra y. In the status of erase suspend, if user wants to read the
data in the secto rs being er ased, the device will o utput status data onto the o utput. Similarly, if pro gram command is
issued after erase suspend, after program operation is completed, system can still read array data in any address
e xcept the sectors to be erased.
The device needs to issue reset co mmand to enable read array operatio n again in order to arbitrarily read the data in
the arra y in the following two situatio ns:
1. In pro gram o r erase o peratio n, the programming o r erasing failure causes Q5 to go high.
2. The de vice is in auto select mode o r CFI mode.
In the two situations above, if reset command is not issued, the device is not in read array mode and system must
issue reset co mmand befo re reading array data.
ACCELERA TED PROGRAM OPERA TION
he device o ffers accelerated program operatio ns through
the ACC function. This is one of two functions provided by the ACC pin. This function is primarily intended to allow
faster manufacturing thro ughput at the factory.
If the system asserts VHH on this pin, the device automatically enters the aforementioned accelerated pro gram mo de,
temporarily unpro tects any protected secto rs , and uses the higher voltage o n the pin to reduce the time required f or
program operations. Removing VHH from the ACC pin must not be at VHH for operations other than accelerated
pro gramming, o r device damage may result.