AS29F400
Preliminary information
Operating modes
®
Mode
CE
OE
L
WE
A0
L
A1
A6
L
A9
RESET
H
DQ
ID read MFR code
ID read device code
Read
L
L
L
H
L
L
L
L
L
H
L
V
V
Code
Code
ID
ID
L
H
H
A0
X
L
L
H
L
H
A1
X
A6
X
A9
X
H
D
OUT
Standby
X
H
H
X
H
High Z
High Z
Output disable
Write
H
X
X
X
X
H
L
A0
L
A1
H
H
H
A6
L
A9
H
D
X
X
IN
Enable sector protect
Sector unprotect
Verify sector protect
V
V
L
Pulse/L
Pulse/L
H
V
V
V
H
ID
ID
ID
ID
ID
L
H
L
H
L
H
Code
Temporary sector
unprotect
X
X
X
X
X
X
X
X
X
X
X
X
X
X
V
L
X
ID
Hardware Reset
High Z
L = Low (<VIL); H = High (>VIH); VID = 12.0 ± 0.5V; X = don’t care; In ×16 mode, BYTE = VIH. In ×8 mode, BYTE = VIL and DQ8–14 is High Z with
DQ15 = A-1(X).
Mode definitions
Item
Description
Selected by A9 = V (11.5–12.5V), CE = OE = A1 = A6 = L, enabling outputs.
ID
ID MFR code,
device code
When A0 is low (V ) the output data = 52h, a unique Mfr. code for Alliance Semiconductor Flash products.
IL
When A0 is high (V ), D
represents the device code for the 29F400.
IH
OUT
Selected with CE = OE = L, WE = H. Data is valid in t
time after addresses are stable, t after CE is low
CE
ACC
Read mode
Standby
and t after OE is low.
OE
Selected with CE = H. Part is powered down, and I reduced to <1.0 mA for TTL input levels and <100 µA
CC
for CMOS levels. If activated during an automated on-chip algorithm, the device completes the operation
before entering standby.
Output disable Part remains powered up; but outputs disabled with OE pulled high.
Selected with CE = WE = L, OE = H. Accomplish all Flash erasure and programming through the command
register. Contents of command register serve as inputs to the internal state machine. Address latching occurs
on the falling edge of WE or CE, whichever occurs later. Data latching occurs on the rising edge WE or CE,
Write
whichever occurs first. Filters on WE prevent spurious noise events from appearing as write commands.
Enable
Hardware protection circuitry implemented with external programming equipment causes the device to
sector protect disable program and erase operations for specified sectors.
Sector
Disables sector protection using external programming equipment.
unprotect
Verifies write protection for sector. Sectors are protected from program/erase operations on commercial
Verify
programming equipment. Determine if sector protection exists in a system by writing the ID read command
sector protect sequence and reading location XXX02h, where address bits A12–17 select the defined sector addresses. A
logical 1 on DQ0 indicates a protected sector; a logical 0 indicates an unprotected sector.
Temporarily disables sector protection for in-system data changes to protected sectors. Apply +12V to RESET
to activate temporary sector unprotect mode. During temporary sector unprotect mode, program protected
sectors by selecting the appropriate sector address. All protected sectors revert to protected state on removal
of +12V from RESET.
Temporary
sector
unprotect
3
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
