Signature Bytes

Calibration Byte in

ATtiny12

ATtiny11/12

•CKSEL3..0 fuses: See Table 3, “Device Clocking Options Select,” on page 10 and Table 10, “ATtiny12 Clock Options and Start-up Times,” on page 25, for which combination of CKSEL3..0 to use. Default value is “0010”, internal RC oscillator with long start-up time.

The status of the fuse bits is not affected by Chip Erase.

Note: 1. If the RSTDISBL Fuse is programmed, then the programming hardware should apply +12V to PB5 while the ATtiny12 is in Power-on Reset. If not, the part can fail to enter programming mode caused by drive contention on PB0 and/or PB5.

All Atmel microcontrollers have a three-byte signature code which identifies the device. The three bytes reside in a separate address space.

For the ATtiny11 they are:

1.$000: $1E (indicates manufactured by Atmel)

2.$001: $90 (indicates 1 Kb Flash memory)

3.$002: $04 (indicates ATtiny11 device when signature byte $001 is $90)

For the ATtiny12(1) they are:

1.$000: $1E (indicates manufactured by Atmel)

2.$001: $90 (indicates 1 Kb Flash memory)

3.$002: $05 (indicates ATtiny12 device when signature byte $001 is $90)

Note: 1. When both lock bits are programmed (Lock mode 3), the Signature Bytes can not be read in the Low-voltage Serial mode. Reading the Signature Bytes will return: $00, $01 and $02.

The ATtiny12 has a one-byte calibration value for the internal RC oscillator. This byte resides in the high byte of address $000 in the signature address space. During memory programming, the external programmer must read this location and program its value into a selected location in the normal Flash or EEPROM Program memory. At start-up, the user software must read this Flash location and write the value to the OSCCAL register.