Yamaha YMF795, Руководство пользователя

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YMF795
-20-
$39h Clock setting
Default: 0000h
Index b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
$39h 0 0 0 0 0 0 0 CLKSET
The register is used to set the clock frequency that is input through the CLK_I pin when the setting is made in the
programmable mode. Be sure to complete the setting before its sound generation.
A clock with any frequency can be input during the reset period.
For details of the clock setting, see “Clock Frequency Setting” (page 24).
CLKSET [8:0] Clock frequency(MHz)
000000000b (Preset mode)
000000001b Prohibition
: :
000101111b Prohibition
000110000b 2.684658000
000110001b 2.740588375
: :
111110001b 27.797396375
111110010b 27.853326750
111110011b Prohibition
: :
111111111b Prohibition
The values that can be set to CLKSET are “000000000b”, and “000110000b” to “111110010b.”
When other value is set, the operation is not guaranteed.
A value to set to CLKSET can be found by using the following formula.
CLKSET = Clock frequency [KHz] / 447.443 × 8
For example, when the clock frequency is 3 MHz:
CLKSET = 3000 / 447.443 × 8 is about 54 = 000110110b
And, actual clock frequency to be set is as follows.
Clock frequency [kHz] = 54 × 447.443 / 8 = 3020.24[kHz] = 3.02024[MHz]