3

AT49F001A(N)(T)

3365C–FLASH–9/03

Device

Operation

READ: The AT49F001A(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 outputs. 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.

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 command 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 com-

mand sequences.

RESET: A RESET input pin is provided to ease some system applications. When RESET is at

a logic high level, the device is in its standard operating mode. A low level on the RESET input

halts the present device operation and puts the outputs of the device in a high impedance

state. If the RESET pin makes a high to low transition during a program or erase operation, the

operation may not be successfully completed and the operation will have to be repeated after

a high level is applied to the RESET pin. When a high level is reasserted on the RESET pin,

the device returns to the read or standby mode, depending upon the state of the control inputs.

By applying a 12V ± 0.5V input signal to the RESET pin, the boot block array can be repro-

grammed even if the boot block lockout feature has been enabled (see Boot Block

Programming Lockout Override section). The RESET feature is not available for the

AT49F001AN(T).

ERASURE: Before a byte can be reprogrammed, the main memory block or parameter block

which contains the byte must be erased. The erased state of the memory bits is a logical “1”.

The entire device can be erased at one time by using a 6-byte software code. The software

chip erase code consists of 6-byte load commands to specific address locations with a specific

data pattern (please refer to the Chip Erase Cycle Waveforms).

After the software chip erase has been initiated, the device will internally time the erase opera-

tion so that no external clocks are required. The maximum time needed to erase the whole

chip is t

not be erased.

CHIP ERASE: If the boot block lockout has been enabled, the Chip Erase function will erase

Parameter Block 1, Parameter Block 2, Main Memory Block 1- 2 but not the boot block. If the

Boot Block Lockout has not been enabled, the Chip Erase function will erase the entire chip.

After the full chip erase the device will return back to read mode. Any command during chip

erase will be ignored.