YMF795 Datasheet, PDF (28/45 Pages) YAMAHA CORPORATION – APL-2 Automobile sound Player-2

YMF795
■Operation in FIFO empty condition
If FIFO become empty during reproduction the musical score data written last is processed continuously until the next
data is written.
If the last data written is a note data, that note is reproduced continuously.
If the last data written is a rest data, the rest state is held.
■Reproduction method assuming occurrence of empty state
In the normal reproduction, occurrence of FIFO Empty is prohibited; however, even simple processing can generate a
short tone if the above features are effectively used. Processing for interrupt is not required.
Make the processing according to the following flow.
Short tone is 1 to 32 word data block.
If data block exceeds 33 words, make the processing by the usual reproduction flow using interrupt.
1) Complete the following procedure in advance: Power ON → Analog Power Down mode → Initialized → STOP
(See the figure of “■State Transition” (page 26).
2) Start the reproduction in the FIFO Empty state.
3) Write the data block to be reproduced into FIFO.
4) Immediately after writing (after 0 to 20µs), the musical score data are internally processed and its reproduction
starts.
As reproduction goes on, the data in FIFO are processed and cleared.
5) When FIFO becomes empty, if the last data in the data block is a note data, that note is reproduced continuously
and if it is a rest data, the rest state is held until the next data block is written into FIFO.
6) When reproducing the next data block, go to step 3).
To stop the reproduction set ST to “0.” Then, the data counter of FIFO will be cleared and the state returns to a
state of step 1).
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