M39432 Datasheet, PDF (19/28 Pages) STMicroelectronics – Single Chip 4 Mbit Flash Memory and 256 Kbit Parallel EEPROM

Figure 14. Write Mode AC Waveforms (EE or EF controlled)
WRITE CYCLE
A0-A18
VALID
tAVEL
tELAX
W
tWLEL
G
E ⁽¹⁾
tGHEL
tELEH
DQ0-DQ7
tDVEH
VALID
RB
tEHWH
tEHGL
tEHEL
tEHDX
tWHRL
M39432
VCC
tVCHWL
Note: 1. E signifies EF when EE = V_IH, and it signifies EE when EF = V_IH.
2. Addresses are latched on the falling edge of E, Data are latched on the rising edge of E.
AI01954
unprotected. Following the protection of a new
sector, the status is found on DQ0 as shown by the
sequence in Figure 8. Following the unprotection
of all sectors, the status is found on DQ0-DQ7 as
shown by the sequence in Figure 9.
These two Verify Sector Protection Status
operations are implemented like Read operations,
but provide a more severe test of the correct
functioning of the device than does a Read Sector
Protection instruction (as shown in Table 4).
Reset Instruction
Reset is an instruction involving either one write
operation or three write operations (as shown in
Table 4).
The Reset instruction returns the memory to its
Read mode, and resets any errors in the Status
Register. If the Reset instruction is issued during a
Sector Erase cycle, or during a Programming
cycle, then the internal logic will take up to 10 µs to
abort. During the abort period, no valid data can be
read from the memory. Issuing a Reset command
during a sector Erase cycle will leave invalid data
in the memory.
GLOSSARY
Block: Flash memory block (4 Mbit) or EEPROM
block (256 Kbit)
Bulk: the whole Flash memory block (4 Mbit)
Sector: 64 KByte of Flash memory
Page: 64 Bytes of EEPROM
Program and Write: Programming (in the Flash
memory block) and Writing (to the EEPROM
block) and are not the same:
s Flash memory bytes are programmed using the
Program instruction (as shown in Table 4). This
is used to change any bit values from ‘1’s to ‘0’s,
where appropriate. As it is impossible to
program bits from ‘0’s to ‘1’s, it is necessary to
run a Sector Erase instruction before any byte
overwriting can be performed.
s EEPROM bytes are written using a simple
operation (Table 3).
SDP: Software Data Protection. This is used for
protecting the EEPROM block against inadvertent
Write operations (for example, in noisy
environments).
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