AM29F800T datasheet(9/41 Pages) AMD

9 / 41 page

8/18/97

Am29F800T/Am29F800B

PR E L IM IN A R Y

In the standby mode the outputs are in the high imped-

ance state, independent of the OE input.

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

Am29F800 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 (see Autoselect Com-

mand Sequence).

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

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

code (Am29F800T = D6H and Am29F800B = 58H for

x8 mode; Am29F800T = 22D6H and Am29F800B =

2258H 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–A18 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.

Am29F800 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–A18

Code (HEX)

Manufacturer Code—AMD

VIL

01H

Am29F800 Device

Am29F800T

Byte

XVIL

VIL

VIH

D6H

Word

22D6H

Am29F800B

Byte

XVIL

VIL

VIH

58H

Word

2258H

Sector Protection

Sector

Address

VIL

VIH

VIL

01H*

Type

Code

Manufacturer Code—AMD

01H

000000

Am29F800

Device

Am29F800T(B)

(W)

D6H

22D6H

A-1

HI-Z

Am29F800B(B)

(W)

58H

2258H

A-1

HI-Z

Sector Protection

01H

000000

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