Joybus Protocol: Difference between revisions
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(→0x00 - Info: known status bytes) |
(→0x05 - Write EEPROM Block: busy status reply) |
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=== 0x05 - Write EEPROM Block === |
=== 0x05 - Write EEPROM Block === |
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If EEPROM is available, this command can be used to write 8 bytes of save data at a time. See "Read EEPROM Block" above for block addressing rules. The 8 bytes of data to write are included in the command immediately following the "block" byte. It may take up to 30 milliseconds for the data to be written to EEPROM. |
If EEPROM is available, this command can be used to write 8 bytes of save data at a time. See "Read EEPROM Block" above for block addressing rules. The 8 bytes of data to write are included in the command immediately following the "block" byte. It may take up to 30 milliseconds for the data to be written to EEPROM. |
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The EEPROM will reply with one byte, 0x80 specifying that the EEPROM was already busy before the write was requested, and 0x00 otherwise. |
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Real EEPROM data storage has inherent unreliability that requires special consideration: EEPROM chips may become corrupted spontaneously due to uncontrollable factors such as power failure during write or memory cell fatigue causing write failures. It is recommended to use a checksum or parity bits in each EEPROM block to check that the data has not been corrupted. EEPROMs used by retail cartridges are rated for up to 100,000 write cycles and may only retain saved data for up to 10 years. Emulators and flashcarts now provide reliable storage for EEPROM commands that do not suffer from these issues. |
Real EEPROM data storage has inherent unreliability that requires special consideration: EEPROM chips may become corrupted spontaneously due to uncontrollable factors such as power failure during write or memory cell fatigue causing write failures. It is recommended to use a checksum or parity bits in each EEPROM block to check that the data has not been corrupted. EEPROMs used by retail cartridges are rated for up to 100,000 write cycles and may only retain saved data for up to 10 years. Emulators and flashcarts now provide reliable storage for EEPROM commands that do not suffer from these issues. |
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