12

Am29F400AT/Am29F400AB

PRELIMINARY

Table 7.

Am29F400A Command Definitions (Notes 1–7)

Notes:

1. Bus operations are defined in Tables 1 and 2.

2. RA = Address of the memory location to be read.

PA = Address of the memory location to be programmed. Addresses are latched on the falling edge of the WE pulse.

SA = Address of the sector to be erased. The combination of A17–A12 will uniquely select any sector.

3. RD = Data read from location RA during read operation.

PD = Data to be programmed at location PA. Data is latched on the rising edge of WE.

4. Reading from non-erasing sectors is allowed in the Erase Suspend mode.

5. Address bits A17–A15 are don’t care for unlock and command cycles.

6. The system should generate the following address patterns:

Word Mode: 5555H or 2AAAH to addresses A0–A14

Byte Mode: AAAAH or 5555H to addresses A-1–A14.

Read/Reset Command

The read or reset operation is initiated by writing the

read/reset command sequence into the command reg-

ister. Microprocessor read cycles retrieve array data

from the memory. The device remains enabled for

reads until the command register contents are altered.

The device will automatically power-up in the read/

reset state. In this case, a command sequence is not

required to read data. Standard microprocessor read

cycles will retrieve array data. This default value en-

sures that no spurious alteration of the memory content

occurs during the power transition. Refer to the AC

Read Characteristics and Waveforms for the specific

timing parameters.

Command

Sequence

Read/Reset

Bus

Write

Cycles

Req’d

First Bus

Write Cycle

Second Bus

Write Cycle

Third Bus

Write Cycle

Fourth Bus

Read/Write Cycle

Fifth Bus

Write Cycle

Sixth Bus

Write Cycle

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Reset/Read

1

XXXXH F0H

Reset/

Read

Word

3

5555H

AAH 2AAAH 55H

5555H

F0H

RA

RD

Byte

AAAAH

5555H

AAAAH

Autoselect

Word

3

5555H

AAH 2AAAH 55H

5555H

90H

01H

2223H

(T Device ID)

22ABH

(B Device ID)

Byte

AAAAH

5555H

AAAAH

23H

(T Device ID)

ABH

(B Device ID)

Word

/Byte

00H

01H (T/B

Manuf. ID)

Program

Word

4

5555H

AAH 2AAAH 55H

5555H

A0H

PA

PD

Byte

AAAAH

5555H

AAAAH

Chip Erase

Word

6

5555H

AAH 2AAAH 55H

5555H

80H

5555H

AAH

2AAAH

55H

5555H

10H

Byte

AAAAH

5555H

AAAAH

AAAAH

5555H

AAAAH

Sector

Erase

Word

6

5555H

AAH 2AAAH 55H

5555H

80H

5555H

AAH

2AAAH

55H

SA

30H

Byte

AAAAH

5555H

AAAAH

AAAAH

5555H

Erase Suspend

1

XXXXH B0H

Erase Resume

1

XXXXH 30H