Yamaha YMF795 Manual page 20

$39h Clock setting
Default: 0000h
Index b15 b14 b13
$39h 0 0
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).
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]
b12 b11 b10 b9
0 0 0 0
CLKSET [8:0]
000000000b
000000001b
:
000101111b
000110000b
000110001b
:
111110001b
111110010b
111110011b
:
111111111b
b8 b7 b6 b5
0
Clock frequency(MHz)
(Preset mode)
Prohibition
:
Prohibition
2.684658000
2.740588375
:
27.797396375
27.853326750
Prohibition
:
Prohibition
-20-
YMF795
b4 b3 b2 b1
CLKSET
b0