Multitap Compatibility Questions
You can use PS1 Multitaps and PS2 Multitaps -check which one yours is. PS1 Multitaps will only work with PS1 games on your PS2.
Generally PS1 controllers work in the PS2 multitap and vice versa with the PS2 controllers working in the PS1 multitap (you might experience a few problems with the Analog and rumble features though).
PS2 memory card will not work in the PS1 Multitap, because the memory cards are on different formats. Also you can't save your PS1 games on a PS2 memory card, so that would stop the PS2 memory card from working in a PS1 Multitap.
Its usually best to stick to official Sony products, but simply plug the Multitap into the Player one port on the PS2 then plug anywhere from 1 to 4 controllers and memory cards into the Multitap. You can also plug in a second Multitap in Player 2 port. However, check the maximum number of players each game will support.
This page should be of help to you, it looks like it can't be done, sorry!!!
http://www.ps2home.co.uk/faq-games.htm