BU94605AKV Datasheet, PDF (48/84 Pages) Rohm – AAC/WMA/MP3 +SD Memory Card +CD-ROM+MP3 Record

BU94605AKV BU94607AKV BU94702AKV BU94705AKV
Datasheet
24. Watchdog Timer
The LSI incorporates Watchdog Timer, which monitors the system hang-up and resets whenever it occurs.
After resetting hang-up, WDT (Watchdog Timer) becomes available. You can disable WDT using DIS_WDT command.
Once WDT is disabled, it cannot be enabled until reset is input.
When WDT, in the valid status, detects a hang-up within the LSI regardless of external situations (on the microcomputer),
the LSI resets the system internally.
To monitor whether the LSI is reset by WDT from the master microcomputer (external), use SET_WDT command to write
H to STATUS WDT_RFLG and monitor this status. After reset, this status is read as L. This helps you judge that WDT
has reset the LSI by reading out L when reading the status regularly after writing H using SET_WDT command.
25. IPL support to external serial FLASH ROM
Once reset, the LSI needs to download the program to a part of the internal program area from the external serial FLASH
ROM.
However, it is also possible to write in data from a microcomputer without connecting external serial FLASH ROM.
The download function from the external serial FLASH ROM enables to add and change the system functions simply by
rewriting the external serial FLASH ROM.
The program is downloaded automatically after reset. After download is completed, it shifts to CONFIG mode.
This LSI supports to serial FLASH ROM to 8 bit-Command, 24 bit-ADDRESS, and clock MIN=15MHz by minimum size
2Mbit. This LSI cannot correspond to serial FLASH ROM that doesn't correspond to Page Program because the data
writing is done with Page Program (256 bytes). This LSI supports to serial FLASH ROM to Write Status Register cycle
time MAX. = 500msec, Page Program cycle time MAX. = 500msec and Chip Erase cycle time MAX. = 180sec.
The download time of the program from serial FLASH ROM is about 0.6 sec. This time changes with contents of the
program write in serial FLASH ROM.
The LSI supports a mode which enables to write the program data written to the memory (USB or SD) to the external
serial FLASH ROM. By executing the command to enable the FLASH ROM write mode, the LSI searches in the
memory and rewrites the external serial FLASH ROM. After rewriting the FLASH ROM, you should reset the LSI.
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2012.12.10 Rev.002