AT29LV020_08 查看數據表（PDF） - Atmel Corporation

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AT29LV020_08

2-megabit (256K x 8) 3-volt Only Flash Memory

Atmel Corporation 

the first data byte has been loaded into the device, successive bytes are entered in the same

manner. Each new byte to be programmed must have its high to low transition on WE (or CE)

within 150 µs of the low to high transition of WE (or CE) of the preceding byte. If a high to low

transition is not detected within 150 µs of the last low to high transition, the load period will end

and the internal programming period will start. A8 to A17 specify the sector address. The sector

address must be valid during each high to low transition of WE (or CE). A0 to A7 specify the byte

address within the sector. The bytes may be loaded in any order; sequential loading is not

required. Once a programming operation has been initiated, and for the duration of tWC, a read

operation will effectively be a polling operation.

4.3 Hardware Data Protection

Hardware features protect against inadvertent programs to the AT29LV020 in the following

ways: (a) VCC sense – if VCC is below 1.8V (typical), the program function is inhibited; (b) VCC

power on delay – once VCC has reached the VCC sense level, the device will automatically time

out 10 ms (typical) before programming; (c) Program inhibit – holding any one of OE low, CE

high or WE high inhibits program cycles; and (d) Noise filter – pulses of less than 15 ns (typical)

on the WE or CE inputs will not initiate a program cycle.

4.4 Input Levels

While operating with a 3.3V ± 10% power supply, the address inputs and control inputs (OE, CE

and WE) may be driven from 0 to 5.5V without adversely affecting the operation of the device.

The I/O lines can be driven from 0 to 3.6V.

4.5 Product Identification

The product identification mode identifies the device and manufacturer as Atmel. It may be

accessed by hardware or software operation. The hardware operation mode can be used by an

external programmer to identify the correct programming algorithm for the Atmel product.

In addition, users may wish to use the software product identification mode to identify the part

(i.e., using the device code), and have the system software use the appropriate sector size for

program operations. In this manner, the user can have a common board design for 256K to

4-megabit densities and, with each density’s sector size in a memory map, have the system soft-

ware apply the appropriate sector size.

For details, see Operating Modes (for hardware operation) or Software Product Identification.

The manufacturer and device code is the same for both modes.

4.6 DATA Polling

The AT29LV020 features DATA polling to indicate the end of a program cycle. During a program

cycle an attempted read of the last byte loaded will result in the complement of the loaded data

on I/O7. Once the program cycle has been completed, true data is valid on all outputs and the

next cycle may begin. DATA polling may begin at any time during the program cycle.

4.7 Toggle Bit

In addition to DATA polling the AT29LV020 provides another method for determining the end of

a program or erase cycle. During a program or erase operation, successive attempts to read

data from the device will result in I/O6 toggling between one and zero. Once the program cycle

has completed, I/O6 will stop toggling and valid data will be read. Examining the toggle bit may

begin at any time during a program cycle.

4 AT29LV020

0565E–FLASH–9/08

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