3

3354F–FLASH–2/05

AT49F002A(N)(T)

3.

Block Diagram

4.

Device Operation

4.1

Read

The AT49F002A(N)(T) is accessed like an EPROM. When CE and OE are low and WE is high,

the data stored at the memory location determined by the address pins is asserted on the out-

puts. The outputs are put in the high impedance state whenever CE or OE is high. This dual-line

control gives designers flexibility in preventing bus contention.

4.2

Command Sequences

When the device is first powered on, it will be reset to the read or standby mode depending upon

the state of the control line inputs. In order to perform other device functions, a series of com-

mand sequences are entered into the device. The command sequences are shown in the

Command Definitions table. The command sequences are written by applying a low pulse on the

WE or CE input with CE or WE low (respectively) and OE high. The address is latched on the

falling edge of CE or WE, whichever occurs last. The data is latched by the first rising edge of

CE or WE. Standard microprocessor write timings are used. The address locations used in the

command sequences are not affected by entering the command sequences.

CONTROL

LOGIC

Y DECODER

PARAMETER

BLOCK 1

(8K BYTES)

BOOT BLOCK

(16K BYTES)

OE

WE

CE

RESET

ADDRESS

INPUTS

VCC

GND

AT49F002A(N)

DATA INPUTS/OUTPUTS

I/O7 - I/O0

8

X DECODER

PARAMETER

BLOCK 2

(8K BYTES)

MAIN MEMORY

BLOCK 1

(32K BYTES)

MAIN MEMORY

BLOCK 2

(64K BYTES)

MAIN MEMORY

BLOCK 3

(64K BYTES)

MAIN MEMORY

BLOCK 4

(64K BYTES)

PROGRAM

DATA LATCHES

Y-GATING

INPUT/OUTPUT

BUFFERS

1FFFF

10000

0FFFF

08000

3FFFF

30000

2FFFF

20000

07FFF

06000

05FFF

04000

03FFF

00000

PARAMETER

BLOCK 1

(8K BYTES)

BOOT BLOCK

(16K BYTES)

AT49F002A(N)T

DATA INPUTS/OUTPUTS

I/O7 - I/O0

8

PARAMETER

BLOCK 2

(8K BYTES)

MAIN MEMORY

BLOCK 1

(32K BYTES)

MAIN MEMORY

BLOCK 2

(64K BYTES)

PROGRAM

DATA LATCHES

Y-GATING

INPUT/OUTPUT

BUFFERS

3FFFF

3C000

3BFFF

3A000

39FFF

38000

37FFF

30000

2FFFF

20000

MAIN MEMORY

BLOCK 3

(64K BYTES)

MAIN MEMORY

BLOCK 4

(64K BYTES)

1FFFF

10000

0FFFF

00000