Q. What must be done to interface TTL to CMOS?

(A) a dropping resistor must be used on the cmos 12 v supply to reduce it to 5 v for the ttl.

(B) as long as the cmos supply voltage is 5 v, they can be interfaced; however, the fan-out of the ttl is limited to five cmos gates.

(C) a 5 v zener diode must be placed across the inputs of the ttl gates in order to protect them from the higher output voltages of the cmos gates.

(D) a pull-up resistor must be used between the ttl output- cmos input node and vcc; the value of rp will depend on the number of cmos gates connected to the node.