ATmega161(L)

Figure 77. Programming the Flash Waveforms

XA1

XA2

BS1

XTAL1

WR

RDY/BSY

RESET +12V

OE

BS2

PAGEL

Figure 78. Programming the Flash Waveforms (Continued)

XA1

XA0

BS1

XTAL1

WR

RDY/BSY

RESET +12V

OE

PAGEL

BS2

Programming the EEPROM The programming algorithm for the EEPROM data memory is as follows (refer to “Programming the Flash” for details on command, address and data loading):

1.A: Load Command “0001 0001”.

2.H: Load Address High Byte ($00 - $01)

3.B: Load Address Low Byte ($00 - $FF)

4.E: Load Data Low Byte ($00 - $FF)

L: Write Data Low Byte

1.Set BS to “0”. This selects low data.

2.Give WR a negative pulse. This starts programming of the data byte. RDY/BSY goes low.

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3.Wait until to RDY/BSY goes high before programming the next byte. (See Figure 79 for signal waveforms.)

The loaded command and address are retained in the device during programming. For efficient programming, the following should be considered:

•The command needs to be loaded only once when writing or reading multiple memory locations.

•Address high byte only needs to be loaded before programming a new 256-word page in the EEPROM.

•Skip writing the data value $FF, that is, the contents of the entire EEPROM after a Chip Erase.

These considerations also apply to Flash, EEPROM and Signature bytes reading.

Figure 79. Programming the EEPROM Waveforms

1.A: Load Command “0000 0010”.

2.H: Load Address High Byte ($00 - $1F)

3.B: Load Address Low Byte ($00 - $FF)

4.Set OE to “0”, and BS1 to “0”. The Flash word low byte can now be read at DATA.

5.Set BS to “1”. The Flash word high byte can now be read at DATA.

6.Set OE to “1”.

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ATmega161(L)

Programming the Fuse Bits The algorithm for programming the Fuse bits is as follows (refer to “Programming the Flash” on page 117 for details on command and data loading):

1.A: Load Command “0100 0000”.

2.C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit. Bit 6 = BOOTRST Fuse bit

Bit 5 = SPIEN Fuse bit

Bit 4 = BODLEVEL Fuse bit Bit 3 = BODEN Fuse bit

Bits 2 - 0 = CKSEL2..0 Fuse bits

Bit 7 = “1”. This bit is reserved and should be left unprogrammed (“1”).

3.Give WR a negative pulse and wait for RDY/BSY to go high.

Programming the Lock Bits The algorithm for programming the Lock bits is as follows (refer to “Programming the Flash” on page 117 for details on command and data loading):

1.A: Load Command “0010 0000”.

2.D: Load Data Low Byte. Bit n = “0” programs the Lock bit. Bit 5 = Boot Lock Bit12

Bit 4 = Boot Lock Bit11 Bit 3 = Boot Lock Bit02 Bit 2 = Boot Lock Bit01 Bit 1 = Lock Bit2

Bit 0 = Lock Bit1

Bits 7 - 6 = “1”. These bits are reserved and should be left unprogrammed (“1”).

3.L: Write Data Low Byte.

The Lock bits can only be cleared by executing Chip Erase.

Reading the Signature Bytes The algorithm for reading the Signature bytes is as follows (refer to “Programming the Flash” on page 117 for details on command and address loading):

1.A: Load Command “0000 1000”.

2.C: Load Address Low Byte ($00 - $02).

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