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**                                                                    **
**          Application notes for Microchip Memory devices            **
**                                                                    **
**                       (Informal Document)                          **
**                                                                    **
**    To find the application notes for your device search for the    **
**    'core' part name.  As an example using the 25HP512 8 pin SOIC   **
**    you would search this document for the entry "25HP512"          **
**                                                                    **
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 25AA160
 ----------
 25LC160
 ----------
 25AA320
 ----------
 25LC320
 ----------
 25AA640
 ----------
 25LC640
 ----------

 There are four levels of Block Protection that can be supported
 on these devices:
                                       Start/End Block
                                       Protection Addresses
                         (BP1), (BP0)  25AA160
 Security Fuse settings:   SF2,   SF1  25LC160
 ------------------------------------  ------------
                             0,     0  None
                             0,     1  $0600->$07FF
                             1,     0  $0400->$07FF
                             1,     1  $0000->$07FF
 ----------------------------------------------------

                                             Start/End Block
                                           Protection Addresses
                         (BP1), (BP0)  25AA320       25AA640
 Security Fuse settings:   SF2,   SF1  25LC320       25LC640
 ------------------------------------  ------------  ------------
                             0,     0  None          None
                             0,     1  $0C00->$0FFF  $1800->$1FFF
                             1,     0  $0800->$0FFF  $1000->$1FFF
                             1,     1  $0000->$0FFF  $0000->$1FFF
 ----------------------------------------------------------------

 Enabling the "Erase EE device" option will ONLY remove all block protection.

 NOTE: The "Erase EE device" option must be enabled when re-programming
       the device in order to remove the Block Protection.

 NOTE: The "Erase EE device" option will NOT Erase the device.
       To re-program the device you must disable Blank/Illegal Bit
       checks flags.

 To program the Hardware Write Protection option (WPEN) enable the
 "Program protect reg." flag.

 Performing a Load operation will also load the Status Register
 Protection Bits into the following address locations in User RAM:
 25AA160  = Address $0800
 25LC160  = Address $0800
 25AA320  = Address $1000
 25LC320  = Address $1000
 25AA640  = Address $2000
 25LC640  = Address $2000

 The Status Register data format in the Programmer's User RAM will
 follow the same format as defined in the corresponding device's
 data sheet, as seen below:

 Status Register Format in relation to the Protection Bits:
  -------------------------------------------------------
 |Bit 7 |Bit 6 |Bit 5 |Bit 4 |Bit 3 |Bit 2 |Bit 1 |Bit 0 |
 |-------------------------------------------------------|
 | WPEN |  X   |  X   |  X   | BP1  | BP0  |  X   |  X   |
  -------------------------------------------------------
 Please refer the manufacturers data sheet for more details.

 NOTE: Checksum issues under TaskLink:
       Performing a LOAD DEVICE operation under TaskLink may produce a
       Checksum that does NOT match the checksum produced during any other
       device operations.  To make sure Checksums match for all operations
       please enable "Use Algorithm Checksum."

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