AM29F400AT datasheet(9/35 Pages) AMD

9 / 35 page

Am29F400AT/Am29F400AB

PRELIMINARY

Output Disable

With the OE input at a logic high level (VIH), output from

the device is disabled. This will cause the output pins to

be in a high impedance state.

Autoselect

The autoselect mode allows the reading of a binary

code from the device and will identify its manufacturer

and type. This mode is intended for use by program-

ming equipment for the purpose of automatically

matching the device to be programmed with its corre-

sponding programming algorithm. This mode is func-

tional over the entire temperature range of the device.

To activate this mode, the programming equipment

must force VID (11.5 V to 12.5 V) on address pin A9.

Two identiﬁer bytes may then be sequenced from the

device outputs by toggling address A0 from VIL to VIH.

All addresses are don’t cares except A0, A1, and A6

(see Table 3).

The manufacturer and device codes may also be read

via the command register, for instances when the

Am29F400A is erased or programmed in a system

without access to high voltage on the A9 pin. The com-

mand sequence is illustrated in Table 4 (see Autoselect

Command Sequence).

Byte 0 (A0 = VIL) represents the manufacturer’s code

(AMD=01H) and byte 1 (A0 = VIH) the device identiﬁer

code (Am29F400AT = 23H and Am29F400AB = ABH

for x8 mode; Am29F400AT = 2223H and Am29F400AB

= 22ABH for x16 mode). These two bytes/words are

given in the table below. All identiﬁers for manufacturer

and device will exhibit odd parity with DQ7 deﬁned as

the parity bit. In order to read the proper device codes

when executing the Autoselect, A1 must be VIL

(see Tables 3 and 4).

The autoselect mode also facilitates the determination

of sector protection in the system. By performing a read

operation at the address location XX02H with the

higher order address bits A12–A17 set to the desired

sector address, the device will return 01H for a pro-

tected sector and 00H for a non-protected sector.

Table 3.

Am29F400A Sector Protection Verify Autoselect Codes

*Outputs 01H at protected sector addresses

Table 4.

Expanded Autoselect Code Table

B) - Byte mode

(W) - Word mode

Type

A12-A17

Code (HEX)

Manufacturer Code-AMD

VIL

01H

Am29F400A Device

Am29F400AT

Byte

XVIL

VIL

VIH

23H

Word

2223H

Am29F400AB

Byte

XVIL

VIL

VIH

ABH

Word

22ABH

Sector Protection

Sector

Address

VIL

VIH

VIL

01H*

Type

Code

Manufacturer Code-AMD

01H

000000

00000001

Am29F400A

Device

Am29F400AT(B)

(W)

23H

2223H

A-1

HI-Z

Am29F400AB(B)

(W)

ABH

22ABH

A-1

HI-Z

Sector Protection

01H

000000

00000001

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