Rainbow Electronics ATtiny15L - Manual (Page 54)

54
ATtiny15L
1187E–AVR–06/02
Memory
Programming
Program and Data
Memory Lock Bits The ATtiny15L MCU provides two Lock bits that can be left unprogrammed, “1”, or can
be programmed, “0”, to obtain the additional features listed in Table 23. The Lock bits
can only be erased with the Chip Erase command
.
Fuse Bits The ATtiny15L has six Fuse bits (BODLEVEL, BODEN, SPIEN, RSTDSBL, and
CKSEL1..0). All the Fuse bits are programmable in both High-voltage and Low-voltage
Serial Programming modes. Changing the Fuses does not have effect while in program-
ming mode.
• The BODLEVEL Fuse selects the Brown-out Detection level and changes the start-
up times. See “Brown-out Detection” on page 17. See Table 5 on page 15. Default
value is programmed “0”.
• When the BODEN Fuse is programed “0”, the Brown-out Detector is enabled. See
“Brown-out Detection” on page 17. Default value is unprogrammed “1”.
• When the SPIEN Fuse bit is programmed “0”, Low-voltage Serial Program and Data
Downloading is enabled. Default value is programmed “0”. Unprogramming this fuse
while in the Low-voltage Serial Programming mode will disable future In-System
downloading attempts.
• When the RSTDISBL Fuse is programmed “0”, the External Reset function of pin
PB5 is disabled
(1) . Default value is unprogrammed “1”. Programming this fuse while
in the Low-voltage Serial Programming mode will disable future In-System
downloading attempts.
• CKSEL1..0 Fuses: See Table 5 on page 15 for which combination of CKSEL1..0 to
use. Default value is “00”, 64 ms + 18 CK.
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 ATtiny15L is in Power-on Reset. If not, the part can fail to enter
Programming mode caused by drive contention on PB0 and/or PB5.
Signature Bytes All Atmel microcontrollers have a three-byte signature code that identifies the device.
The three bytes reside in a separate address space, and for the ATtiny15L they are:
1. $000 : $1E (indicates manufactured by Atmel).
2. $001 : $90 (indicates 1 Kb Flash memory).
3. $002 : $06 (indicates ATtiny15L device when $001 is $90).
Table 23. Lock Bit Protection Modes
Memory Lock Bits
Protection Type Mode LB1 LB2
1 1 1 No memory lock features enabled.
2 0 1 Further programming of the Flash and EEPROM is disabled.
3 0 0 Same as mode 2, but verify is also disabled.