FLASH
Austin Semiconductor, Inc.
Standby Mode
When the system is not reading or writing to the device, it
can place the device in the standby mode. In this mode, current
consumption is greatly reduced, and the outputs are placed in
the high impedance state, independent of the OE\ input.
The device enters the CMOS standby mode when the CE\
pin is held at V
CC
± 0.5V. (Note that this is a more restricted
voltage range than V
IH
.) The device enters the TTL standby
mode when CE\ is held at V
IH
. The device requires the standard
access time (t
CE
) before it is ready to read data.
If the device is deselected during erasure or programming,
the device draws active current until the operation is completed.
I
CC3
in the DC Characteristics table represents the standby
current specification.
AS29F040
Definitions table shows the remaining address bits that are
don’t care. When all necessary bits have been set as required,
the programming equipment may then read the corresponding
identifier code on DQ7 - DQ0
To access the autoselect codes in-system, the host system
can issue the autoselect command via the command register, as
shown in the Command Definitions table. This method does
not require V
ID
. See “Command Definitions” for details on
using the autoselect mode.
Sector Protection/Unprotection
The hardware sector protection feature disables both
program and erase operations in any sector. The hardware
sector unprotection feature re-enables both program and erase
operations in previously protected sectors.
Sector protection/unprotection must be implemented
using programming equipment. The procedure requires a high
voltage (V
ID
) on address pin A9 and the control pins. The
device is shipped with all sectors unprotected. It is possible to
determine whether a sector is protected or unprotected. See
“Autoselect Mode” for details.
Output Disable Mode
When the OE\ input is at V
IH
, output from the device is
disabled. The output pins are placed in the high impedance
state.
Autoselect Mode
The autoselect mode provides manufacturer and device
identification, and sector protection verification, through
identifier codes output on DQ7 - DQ0. This mode is primarily
intended for programming equipment to automatically match a
device to be programmed with its corresponding programming
algorithm. However, the autoselect codes can also be accessed
in-system through the command register.
When using programming equipment, the autoselect mode
requires V
ID
(11.5V to 12.5 V) on address pin A9. Address pins
A6, A1, and A0 must be as shown in the Autoselect Codes
(High Voltage Method) table. In addition, when verifying
sector protection, the sector address must appear on the
appropriate highest order address bits. Refer to the
corresponding Sector Address Tables. The Command
Hardware Data Protection
The command sequence requirement of unlock cycles for
programming or erasing provides data protection against
inadvertent writes (refer to the Command Definitions table). 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
CC
power-up and power-down transitions, or from system
noise.
Low V
CC
Write Inhibit
When V
CC
is less than V
LKO
, the device does not accept
any write cycles. This protects data during V
CC
power-up and
TABLE 2: SECTOR ADDRESSES TABLE
SECTOR
SA0
SA1
SA2
SA3
SA4
SA5
SA6
SA7
NOTE:
AS29F040
Rev. 2.2 09/07
A18
0
0
0
0
1
1
1
1
A17
0
0
1
1
0
0
1
1
A16
0
1
0
1
0
1
0
1
ADDRESS RANGE
00000h - 0FFFFh
10000h - 1FFFFh
20000h - 2FFFFh
30000h - 3FFFFh
40000h - 4FFFFh
50000h - 5FFFFh
60000h - 6FFFFh
70000h - 7FFFFh
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
All sectors are 64 Kbytes in size.
5
AUSTIN [ AUSTIN SEMICONDUCTOR ]
