YMF795 Datasheet, PDF (24/45 Pages) YAMAHA CORPORATION – APL-2 Automobile sound Player-2

YMF795
■On Reset
This LSI can be initialized by setting /RST pin to “L.” And, CLR bit is provided in $32h to allow the software to
initialize the LSI.
Hardware reset initializes the LSI and returns it to the default condition.
All the registers except the timbre data register of Index 10h to 2Fh are initialized by the software reset.
A counter for the amount of FIFO data is cleared to “Empty” state.
Input of CLK_I is required during reset. Be sure to control so that CLK_I is input at least more than 100 clocks during
the reset.
After the reset cancellation, access a register after waiting at least 64 clocks of CLK_I.
■Settings and Procedure required for a piece generation
Necessary settings and procedure are as follows.
1. Set the CLKSEL ($33h) or CLKSEL ($39h) according to the clock frequency inputted for CLK_I.
2. Cancel the power-down mode of the analog section. (See “Cautions for cancellation of the power-down” (page22).
3. Set the timbre data ($10-2Fh), timbre allocation data ($30h), tempo data ($31h) and volumes ($35-37h) as required.
4. Write musical score data ($00h) for 32 data (that is, to FIFO_FULL).
5. Set the IRQ point value of $34h.
6. Set the IRQE of $34h to “1.”
7. Set the ST bit of $32h to “1” to start the melody.
■Clock Frequency Setting
Two modes for clock frequency setting are supported: “Preset mode” and “Programmable Mode.”
Preset mode: a clock is selected from 2.688 / 8.4 / 12.6 / 14.4 /19.2 / 19.68 / 19.8 / 27.82 MHz.
Programmable mode: a clock is selected from 2.685 MHz to 27.853 MHz in 55.93 kHz steps.
1) When the preset mode is used:
Clock frequency setting can be made in the preset mode by setting a value to $33h.
In this case, set $39h to “000000000b.” Operation is not guaranteed if other value is set.
When a value is not set to both $33h and $39h (default condition), a condition that 2.688 MHz is set in the preset
mode is given.
2) When the programmable mode is used:
Clock frequency setting can be made in the programmable mode by setting a value to $39h.
In this case, set $33h to “000b.” Operation is not guaranteed if other value is set.
A value that can be set to $39h is “000000000b” and “000110000b” to “111110010b.”
Operation is not guaranteed if other value is set.
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