Rainbow Electronics AT90LS4433 - Manual (Page 85)

85
AT90S/LS4433
1042G–AVR–09/02
Memory
Programming
Program and Data
Memory Lock Bits The AT90S4433 MCU provides two Lock bits, which can be left unprogrammed (“1”) or
can be programmed (“0”) to obtain the additional features listed in Table 28. The Lock
bits can only be erased with the Chip Erase command.
Note: 1. In Parallel mode, programming of the Fuse bits are also disabled. Program the Fuse
bits before programming the Lock bits.
Fuse Bits The AT90S4433 has six Fuse bits, SPIEN, BODLEVEL, BODEN and CKSEL2..0.
• When the SPIEN Fuse is programmed (“0”), Serial Program and Data Downloading
is enabled. Default value is programmed (“0”). This bit is not accessible in Serial
Programming mode.
• The BODLEVEL Fuse selects the Brown-out Detection Level and changes the start-
up times. See “Brown-out Detection” on page 25. Default value is unprogrammed
(“1”).
• When the BODEN Fuse is programmed (“0”), the Brown-out Detector is enabled.
See “Brown-out Detection” on page 25. Default value is unprogrammed (“1”).
• CKSEL2..0: See Table 5 on page 23 for which combination of CKSEL2..0 to use.
Default value is “010”.
Signature Bytes All Atmel microcontrollers have a 3-byte signature code that identifies the device. This
code can be read in both serial and parallel mode. The three bytes reside in a separate
address space.
For the AT90S4433 (1) they are:
1. $000: $1E (indicates manufactured by Atmel)
2. $001: $92 (indicates 4 KB Flash memory)
3. $002: $03 (indicates AT90S4433 device when signature byte $001 is $92)
Note: 1. When both Lock bits are programmed (Lock mode 3), the signature bytes cannot be
read in Serial mode. Reading the signature bytes will return $00, $01 and $02.
Table 28. 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.
(1)
3 0 0 Same as mode 2, and verify is also disabled.