FPGAs can be used to chain multiple logic gates together in a compact manner. They come with 4 I/O ports and 10 internal registers, which can then be connected with each other to form logic circuits. They work fine in unloaded blocks.
Supported gate types: AND, OR, NOT, XOR, NAND, XNOR, Buffer (=)
I/O ports: A B C D; Registers: numbered 0 to 9