ΜPD7755C/µPD7756C pinout
NEC µPD7755, µPD7756: 18-pin 0.3" DIP (used with mappers 18, 72, 86, and 92)
.--V--.
I4 -> |01 18| <- I3
I5 -> |02 17| <- I2
I6 -> |03 16| <- I1
I7 -> |04 15| <- I0
Iref -> |05 14| <- /START
SOUND <- |06 13| <- /CS
/BUSY <- |07 12| <- X1
/RST -> |08 11| -> X2
Gnd -- |09 10| -- Vdd
'-----'
The amount of current flowing into Iref specifies the amount of current flowing into the SOUND output when the DAC is set to 16 (1/32nd full scale). This is usually configured with an external resistor.
X1 and X2 should be hooked up to a 640kHz ceramic resonator.