ATtiny5 datasheet(114/168 Pages) ATMEL

114 / 168 page

114

8127C–AVR–10/09

ATtiny4/5/9/10

15.4.4

Reading NVM Lock Bits

The Non-Volatile Memory Lock Byte can be read from the mapped location in data memory.

15.4.5

Writing NVM Lock Bits

The algorithm for writing the Lock bits is as follows.

1. Write the WORD_WRITE command to the NVMCMD register.

2. Write the lock bits value to the Non-Volatile Memory Lock Byte location. This is the low

byte of the Non-Volatile Memory Lock Word.

3. Start the NVM Lock Bit write operation by writing a dummy byte to the high byte of the

NVM Lock Word location.

4. Wait until the NVMBSY bit has been cleared.

15.5 Self programming

The ATtiny4/5/9/10 don't support internal programming.

15.6 External Programming

The method for programming the Non-Volatile Memories by means of an external programmer is

referred to as external programming. External programming can be done both in-system or in

mass production.

The Non-Volatile Memories can be externally programmed via the Tiny Programming Interface

(TPI). For details on the TPI, see “Programming interface” on page 96. Using the TPI, the exter-

nal programmer can access the NVM control and status registers mapped to I/O space and the

NVM memory mapped to data memory space.

15.6.1

Entering External Programming Mode

The TPI must be enabled before external programming mode can be entered. The following pro-

cedure describes, how to enter the external programming mode after the TPI has been enabled:

1. Make a request for enabling NVM programming by sending the NVM memory access

key with the SKEY instruction.

2. Poll the status of the NVMEN bit in TPISR until it has been set.

Refer to the Tiny Programming Interface description on page 96 for more detailed information of

enabling the TPI and programming the NVM.

15.6.2

Exiting External Programming Mode

Clear the NVM enable bit to disable NVM programming, then release the RESET pin.

See NVMEN bit in “TPISR – Tiny Programming Interface Status Register” on page 106.

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