YMF795 Datasheet, PDF (37/45 Pages) YAMAHA CORPORATION – APL-2 Automobile sound Player-2

YMF795
■Serial I/F Specifications
8 clk
SCLK
16 clk
SYNC
Type1
SYNC
Type2
SDIN
MSB
76
LSB
10
Index Data (8bit)
MSB
LSB
15
10
Control Data (16bit)
MSB
76
YMF795 is controlled by the three serial interface lines of SCLK, SYNC, and SDIN.
Relation between SDIN and SCLK
The LSI takes in the value of SDIN at the rising edge of SCLK.
Input the SDIN so that Setup/Hold time is assured with respect to the rising edge of SCLK.
(For details of timing specification, see “4. AC characteristics” in “Electric Characteristics”)
About SDIN
The above figure has the period at which no data is transferred between Index data and Control data, but this period
is not necessarily required. Data of 24-bit can be transferred in succession.
When transfer in 8 bits is required, divide the Control data in two of high-order 8 bits and low-order 8 bits. The
interval between the first high-order 8 bits and the next low-order 8 bits transfer is not especially defined. However,
if excessive interval is given, time taken to complete one transfer becomes long. Pay attention so that FIFO does
not become empty when writing the musical score data into the FIFO.
About SYNC
Both Type1 and Type2 in the above figure are available.
The LSI considers the rising edge of SYNC as the completion of one data transfer..
The LSI sees SDIN for 24×SCLK before the rising edge of SYNC as valid data.
(SDIN for 16×SCLK are valid data when only Control Data is transferred.)
The length of the period of “H” is not especially defined, but for the waveform of Type 2, control so that the period
of “L” is assured at least 100 ns.
Malfunction may be caused when a rising edge of SYNC comes close to a rising edge of SCLK.
Consider so that a rising edge of SCLK does not generate within 50ns with respect to a rising edge of SYNC.
About the data transfer only Control Data.
When the SDIN for SCLK×16 is input between a rising edge of SYNC and the next rising edge of SYNC, the LSI
judges it as the musical score data ($00h) to take it in.
Use this transfer when transferring musical score data fast.
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