block diagram showin 74LS138 being used with Z80

i have i slight problem, and its got me stumped

i need to produce a block diagram for a simple mircoprocessor system,

showing how a 74LS138 logic device could be used as part of the

address decoding, if 4 * 1 Kbyte memory devices are to be used with a

Z80 CPU

normally i dont like asking but this i just cant figure out or find on

the net.

any help would be apprecaited

thanks for your help