AT89LP51 datasheet(85/113 Pages) ATMEL

85 / 113 page

3709C–MICRO–5/11

AT89LP51/52 - Preliminary

7. Atmel Signature Bytes:

8. Symbol Key:

17.4

Status Register

The current state of the memory may be accessed by reading the status register. The status reg-

ister is shown in Table 17-3.

17.5

DATA Polling

The AT89LP51/52 implements DATA polling to indicate the end of a programming cycle. While

the device is busy, any attempted read of the last byte written will return the data byte with the

MSB complemented. Once the programming cycle has completed, the true value will be acces-

sible. During Erase the data is assumed to be FFH and DATA polling will return 7FH. When

writing multiple bytes in a page, the DATA value will be the last data byte loaded before pro-

gramming begins, not the written byte with the highest physical address within the page.

17.6

Flash Security

The AT89LP51/52 provides three Lock Bits for Flash Code and Data Memory security. Lock bits

can be left unprogrammed (FFh) or programmed (00h) to obtain the protection levels listed in

Table 17-4. Lock bits can only be erased (set to FFh) by Chip Erase. Lock bit mode 2 disables

programming of all memory spaces, including the User Signature Array and User Configuration

Fuses. User fuses must be programmed before enabling Lock bit mode 2 or 3. Lock bit mode 3

Address:

0000H

0001H

0002H

AT89LP51:

1EH

54H

05H

AT89LP52:

1EH

54H

06H

a:Page Address Bit

s:Half Page Select Bit

Byte Address Bit

Don’t Care Bit

Table 17-3.

Status

–

––

–

LOAD

SUCCESS

WRTINH

BUSY

Bit

543

Symbol

Function

LOAD

Load flag. Cleared low by the load page buffer command and set high by the next memory write. This flag signals that

the page buffer was previously loaded with data by the load page buffer command.

SUCCESS

Success flag. Cleared low at the start of a programming cycle and will only be set high if the programming cycle

completes without interruption from the brownout detector.

WRTINH

Write Inhibit flag. Cleared low by the brownout detector (BOD) whenever programming is inhibited due to V

DD falling

below the minimum required programming voltage. If a BOD episode occurs during programming, the SUCCESS flag

will remain low after the cycle is complete.

BUSY

Busy flag. Cleared low whenever the memory is busy programming or if write is currently inhibited.

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