ATtiny28L Atmel Corporation, ATtiny28L Datasheet - Page 46
Manufacturer Part Number
Specifications of ATtiny28L
Max. Operating Frequency
Hardware Qtouch Acquisition
Max I/o Pins
Resistive Touch Screen
Self Program Memory
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Mpu / Mmu
no / no
Calibrated Rc Oscillator
Program Memory Lock
The ATtiny28 MCU provides two Lock bits that can be left unprogrammed (“1”) or can be
programmed (“0”) to obtain the additional features listed in Table 20. The Lock bits can
only be erased with the Chip Erase command.
Table 20. Lock Bit Protection Modes
Memory Lock Bits
No memory lock features enabled.
Further programming of the Flash is disabled.
Same as mode 2, and verify is also disabled.
1. Further programming of the Fuse bits is also disabled. Program the Fuse bits before
programming the Lock bits.
The ATtiny28 has five Fuse bits, INTCAP and CKSEL3..0.
When the INTCAP Fuse is programmed (“0”), internal load capacitors are
connected between XTAL1/XTAL2 and GND, similar to C1 and C2 in Figure 5. See
“Crystal Oscillator” on page 7. Default value is unprogrammed (“1”).
CKSEL3..0 Fuses: See Table 1, “Device Clocking Option Select,” on page 7 and
Table 5, “ATtiny28 Clock Options and Start-up Time,” on page 16, 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.
All Atmel microcontrollers have a 3-byte signature code that identifies the device. The
three bytes reside in a separate address space.
For the ATtiny28, they are:
1. $000: $1E (indicates manufactured by Atmel)
2. $001: $91 (indicates 2 KB Flash memory)
3. $002: $07 (indicates ATtiny28 device when signature byte $001 is $91)
The ATtiny28 has 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 it into a
selected location in the the normal Flash program memory. At start-up, the user soft-
ware must read this Flash location and write the value to the OSCCAL register.