Table 3 — Commands Definitions
Command
Sequence
Read/Reset
Byte Program
Chip Erase
Sector Erase
Bus
Write
Cycle
Req’d
4
6
6
6
First Bus Write Second Bus Write Third Bus Write
Cycle
Cycle
Cycle
Addr
5555H
5555H
5555H
5555H
Data
AAH
AAH
AAH
AAH
Addr
2AAAH
2AAAH
2AAAH
2AAAH
Data
55H
55H
55H
55H
Addr
5555H
5555H
5555H
5555H
Data
F0H
A0H
80H
80H
Fourth Bus
Read/Write
Cycle
Addr
RA
PA
5555H
5555H
Data
RD
PD
AAH
AAH
2AAAH
2AAAH
55H
55H
5555H
SA
10H
30H
Fifth Bus Write Sixth Bus Write
Cycle
Cycle
Addr
Data
Addr
Data
NOTES:
1. Address bit A15 = X = Don't Care. Write Sequences may be initiated with A15 in either state.
2. Address bit A16 = X = Don't Care for all address commands except for Program Address (PA) and Sector Address (SA).
3. RA = Address of the memory location to be read
PA = Address of the memory location to be programmed. Addresses are latched on the falling edge of the WE pulse.
SA = Address of the sector to be erased. The combination of A16, A15, A14 will uniquely select any sector.
4. RD = Data read from location RA during read Operation.
PD = Data to be programmed at location PA. Data is latched on the rising edge of WE.
default value ensures that no spurious alteration of the
memory content occurs during the power transition.
Refer to the AC Read Characteristics and Figure 7 for the
specific timing parameters.
CHIP ERASE
Chip erase is a six bus cycle operation. There are two
'unlock' write cycles. These are followed by writing the
“set-up” command. Two more “unlock” write cycles are
then followed by the chip erase command.
Chip erase does not require the user to program the
device prior to erase. Upon executing the Embedded
Erase Algorithm command sequence (Figure 4) the
device will automatically program and verify the entire
memory for an all zero data pattem prior to electrical
erase. The erase is performed concurrently on all sectors
at the same time . The system is not required to provide
any controls or timings during these operations.
Note:
Post Erase data state is all "1"s.
The automatic erase begins on the rising edge of the last
WE pulse in the command sequence and terminates
when the data on D7 is "1" (see Write Operation Status
section - Table 3) at which time the device retums to read
mode. See Figures 4 and 9.
BYTE PROGRAMING
The device is programmed on a byte-byte basis.
Programming is a four bus cycle operation. There are
two "unlock" write cycles. These are followed by the
program set-up command and data write cycles.
Addresses are latched on the falling edge of CE or WE,
whichever occurs later, while the data is latched on the
rising edge of CE or WE whichever occurs first. The
rising edge of CE or WE (whichever happens first) begins
programming using the Embedded Program Algorithm.
Upon executing the program algorithm command
sequence the system is
not
required to provide further
controls or timings. The device will automatically provide
adequate internally generated program pulses and verify
the programmed cell.
The automatic programming operation is completed
when the data on D
7 (
also used as Data Polling) is
equivalent to data written to this bit at which time the
device returns to the read mode and addresses are no
longer latched. Therefore, the device requires that a valid
address be supplied by the system at this particular
instance of time for Data Polling operations. Data Polling
must be performed at the memory location which is being
programmed.
Any commands written to the chip during the Embedded
Program Algorithm will be ignored.
Programming is allowed in any sequence and across
sector boundaries. Beware that a data "0" cannot be
programmed back to a “1". Attempting to do so may
cause the device to exceed programming time limits (D5
= 1) or result in an apparent success, according to the
data polling algorithm, but a read from reset/read mode
will show that the data is still “0". Only erase operations
can convert “0"s to “1"s.
Figure 3 illustrates the programming algorithm using
typical command strings and bus operations.
SECTOR ERASE
Sector erase is a six bus cycle operation. There are two
"unlock" write cycles. These are followed by writing the
"setup" command. Two more "unlock" write cycles are
then followed by the sector erase command. The sector
address (any address location within the desired sector)
is latched on the falling edge of WE, while the command
(30H) is latched on the rising edge of WE. After a
time-out of 80µs from the rising edge of the last sector
erase command, the sector erase operation will begin.
Multiple sectors may be erased concurrently by writing
the six bus cycle operations as described above. This
sequence is followed with writes of the sector erase
command to addresses in other sectors desired to be
concurrently erased. The time between writes must be
less than 80µs otherwise that command will not be
accepted and erasure will start. It is recommended that
processor interrupts be disabled during this time to
guarantee this condition.
The interrupts can be
re-enabled after the last Sector Erase command is
written. A time-out of 80µs from the rising edge of the
last WE will initiate the execution of the Sector Erase
command(s). If another falling edge of the WE occurs
6
Aeroflex Circuit Technology
SCD1667 REV A 4/28/97 Plainview NY (516) 694-6700
AEROFLEX [ AEROFLEX CIRCUIT TECHNOLOGY ]
