Table 1. Am29F040 User Bus Operations
Operation
Autoselect Manufacturer Code (Note 1)
Autoselect Device Code (Note 1)
Read (Note 4)
CE
L
OE
L
WE
H
A0
L
A1
L
A6
L
A9
I/O
Code
V
ID
L
L
H
H
L
L
V
Code
ID
L
L
H
A0
X
A1
X
A6
X
A9
X
RD
Standby
H
L
X
H
H
L
X
HIGH Z
HIGH Z
PD (Note 2)
Code
Output Disable
H
X
X
X
X
Write
L
L
A0
L
A1
H
A6
L
A9
Verify Sector Protect (Note 3)
Autoselect Device Unprotect Code
L
H
V
ID
L
L
H
H
H
L
V
Code
ID
Legend:
L = Logic 0, H = Logic 1, X = Don’t Care. See DC Characteristics for voltage levels.
Notes:
1. Manufacturer and device codes may also be accessed via a command register write sequence. Refer to Tables 2 and 4.
2. Refer to Table 3 for valid PD (Program Data) during a write operation.
3. Refer to the section on Sector Protection.
4. WE can be V if OE is V , OE at V initiates the write operations.
IL
IL
IH
Read Mode
Output Disable
The Am29F040 has two control functions which must
be satisfied in order to obtain data at the outputs. CE is
the power control and should be used for device selec-
tion. OE is the output control and should be used to
gate data to the output pins if a device is selected.
With the OE input at a logic high level (V ), output from
the device is disabled.This will cause the output pins to
be in a high impedance state.
IH
Autoselect
The autoselect mode allows the reading out of a binary
code from the device and will identify its manufacturer
and type.This mode is intended for use by programming
equipment for the purpose of automatically matching the
device to be programmed with its corresponding pro-
gramming algorithm. This mode is functional over the
entire temperature range of the device.
Address access time (t
stable addresses to valid output data. The chip enable
) is equal to the delay from
ACC
access time (t ) is the delay from stable addresses and
CE
stable CE to valid data at the output pins.The output en-
able access time is the delay from the falling edge of OE
to valid data at the output pins (assuming the addresses
have been stable for at least t
–t time).
ACC OE
To activate this mode, the programming equipment
Standby Mode
must force V (11.5 V to 12.5 V) on address pin A9.
ID
The Am29F040 has two standby modes, a CMOS
Two identifier bytes may then be sequenced from the
standby mode (CE input held at V ± 0.5 V), when the
device outputs by toggling address A0 from V to V .
CC
IL IH
current consumed is less than 5 µA; and a TTL standby
All addresses are don’t cares except A0, A1, and A6.
mode (CE is held at V ) when the current required is
IH
The manufacturer and device codes may also be read
via the command register, for instances when the
Am29F040 is erased or programmed in a system with-
out access to high voltage on the A9 pin.The command
sequence is illustrated in Table 4 (refer to Autoselect
Command section).
reduced to approximately 1 mA. In the standby mode
the outputs are in a high impedance state, independent
of the OE input.
If the device is deselected during erasure or program-
ming, the device will draw active current until the
operation is completed.
Byte 0 (A0 = V ) represents the manufacturer’s code
IL
(AMD = 01H) and byte 1 (A0 = V ) the device identifier
IH
code (Am29F040 = A4H). All identifiers for manufac-
turer and device exhibit odd parity with the MSB (DQ7)
defined as the parity bit. See Table 2.
Am29F040
7
AMD [ AMD ]
