COM (Ternary Gate)

Compare

Uses

This gate is biased towards the A input. Only when A is zero does B have any effect.

A tree of compares can compute if a register is negative, zero, or positive. This is done as part of the ALU Flags.

Truth Tables

COM

COM		B
		-	0	+
A	-	-	-	-
	0	-	0	+
	+	+	+	+

COM
A	B	Y
-	-	-
-	0	-
-	+	-
0	-	-
0	0	0
0	+	+
+	-	+
+	0	+
+	+	+

---

NCOM

NCOM		B
		-	0	+
A	-	+	+	+
	0	+	0	-
	+	-	-	-

NCOM
A	B	Y
-	-	+
-	0	+
-	+	+
0	-	+
0	0	0
0	+	-
+	-	-
+	0	-
+	+	-