AM29PDL640G AMD [Advanced Micro Devices], AM29PDL640G Datasheet - Page 25

• Manufacturer Part Number: AM29PDL640G
• Description: 64 Megabit (4 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Read/Write Flash Memory with Enhanced VersatileIOTM Control
• Manufacturer: AMD [Advanced Micro Devices]

that the accelerated programming (ACC) and unlock
bypass functions are not available when programming
the SecSi Sector.
The SecSi Sector area can be protected using one of
the following procedures:
■ Write the three-cycle Enter SecSi Sector Region
■ To verify the protect/unprotect status of the SecSi
Once the SecSi Sector is locked and verified, the sys-
tem must write the Exit SecSi Sector Region com-
mand sequence to return to reading and writing the
remainder of the array.
The SecSi Sector lock must be used with caution
since, once locked, there is no procedure available for
unlocking the SecSi Sector area and none of the bits
in the SecSi Sector memory space can be modified in
any way.
SecSi Sector Protection Bit
The SecSi Sector Protection Bit prevents program-
ming of the SecSi Sector memory area. Once set, the
SecSi Sector memory area contents are non-modifi-
able.
December 13, 2005
command sequence, and then follow the in-system
sector protect algorithm as shown in Figure Note:,
except that RESET# may be at either V
This allows in-system protection of the SecSi Sector
Region without raising any device pin to a high volt-
age. Note that this method is only applicable to the
SecSi Sector.
Sector, follow the algorithm shown in Figure 3.
Figure 3. SecSi Sector Protect Verify
Write 40h to SecSi
Read from SecSi
Sector address
Sector address
A1 = 1, A0 = 0
A1 = 1, A0 = 0
Write 60h to
with A6 = 0,
any address
with A6 = 0,
RESET# =
V
Wait 1 μs
START
IH
or V
ID
Remove V
SecSi Sector is
SecSi Sector is
If data = 00h,
If data = 01h,
from RESET#
Protect Verify
SecSi Sector
unprotected.
Write reset
protected.
command
complete
IH
or V
ID
D A T A S H E E T
IH
or V
Am29PDL640G
ID
.
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadvertent writes. In addition, the following
hardware data protection measures prevent accidental
erasure or programming, which might otherwise be
caused by spurious system level signals during V
power-up and power-down transitions, or from system
noise.
Low V
When V
cept any write cycles. This protects data during V
power-up and power-down. The command register
and all internal program/erase circuits are disabled,
and the device resets to the read mode. Subsequent
writes are ignored until V
system must provide the proper signals to the control
pins to prevent unintentional writes when V
greater than V
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE#, CE#
or WE# do not initiate a write cycle.
Logical Inhibit
Write cycles are inhibited by holding any one of OE# =
V
CE# and WE# must be a logical zero while OE# is a
logical one.
Power-Up Write Inhibit
If WE# = CE# = V
the device does not accept commands on the rising
edge of WE#. The internal state machine is automati-
cally reset to the read mode on power-up.
COMMON FLASH MEMORY INTERFACE
(CFI)
The Common Flash Interface (CFI) specification out-
lines device and host system software interrogation
handshake, which allows specific vendor-specified
software algorithms to be used for entire families of
devices. Software support can then be device-inde-
pendent, JEDEC ID-independent, and forward- and
backward-compatible for the specified flash device
families. Flash vendors can standardize their existing
interfaces for long-term compatibility.
This device enters the CFI Query mode when the sys-
tem writes the CFI Query command, 98h, to address
55h, any time the device is ready to read array data.
The system can read CFI information at the addresses
given in Tables 10–13. To terminate reading CFI data,
the system must write the reset command. The CFI
Query mode is not accessible when the device is exe-
IL
, CE# = V
CC
CC
Write Inhibit
is less than V
IH
LKO
or WE# = V
.
IL
and OE# = V
LKO
CC
IH
, the device does not ac-
is greater than V
. To initiate a write cycle,
IH
during power up,
LKO
. The
CC
23
CC
CC
is