Rainbow Electronics AT90S8515 - Manual (Page 78)

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AT90S8515
0841G–09/01
Memory
Programming
Program and Data
Memory Lock Bits The AT90S8515 MCU provides two Lock bits that can be left unprogrammed (“1”) or can
be programmed (“0”) to obtain the additional features listed in Table 25. The Lock bits
can only be erased with the Chip Erase command.
Note: 1. In Parallel Mode, further programming of the Fuse bits is also disabled. Program the
Fuse bits before programming the Lock bits.
Fuse Bits The AT90S8515 has two Fuse bits, SPIEN and FSTRT.
• When the SPIEN Fuse is programmed (“0”), Serial Program and Data Downloading
is enabled. Default value is programmed (“0”).
• When the FSTRT Fuse is programmed (“0”), the short start-up time is selected.
Default value is unprogrammed (“1”). Parts with this bit pre-programmed (“0”) can
be delivered on demand.
The Fuse bits are not accessible in Serial Programming Mode. The status of the Fuse
bits is not affected by Chip Erase.
Signature Bytes All Atmel microcontrollers have a three-byte signature code that identifies the device.
This code can be read in both Serial and Parallel mode. The three bytes reside in a sep-
arate address space.
For the AT90S8515 (1) they are:
1. $000: $1E (indicates manufactured by Atmel)
2. $001: $93 (indicates 8 KB Flash memory)
3. $002: $01 (indicates AT90S8515 device when signature byte $001 is $93)
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.
Programming the Flash
and EEPROM Atmel’s AT90S8515 offers 8K bytes of In-System Reprogrammable Flash program
memory and 512 bytes of EEPROM data memory.
The AT90S8515 is shipped with the On-chip Flash program and EEPROM data memory
arrays in the erased state (i.e., contents = $FF) and ready to be programmed. This
device supports a high-voltage (12V) Parallel Programming Mode and a low-voltage
Serial Programming Mode. The +12V is used for programming enable only, and no cur-
rent of significance is drawn by this pin. The Serial Programming Mode provides a
convenient way to download program and data into the AT90S8515 inside the user’s
system.
The program and data memory arrays on the AT90S8515 are programmed byte-by-byte
in either programming mode. For the EEPROM, an auto-erase cycle is provided within
Table 25. 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.