For those of you who aren't familiar. I just ripped this from RGP but I believe it was in Clay's guide as well:
the NBA Fastbreak link option is done
through the A/V board's serial port. Installing a serial port on
WPC-95 games is easy, and you can save the money by doing it yourself
instead of buying the kit. The WPC-95 A/V board comes with those two
serial port chips missing by default, so these chips will need to be
purchased and insert them into positions U22 and U24 on the WPC-95 A/V
board. U22 is a MAX239 RS-232 driver chip, and U24 is a 16C450 UART.
Digi-Key (www.digikey.com) is currently selling the MAX239 for $7.55
and the 16C450 for $5.60 (using a buffered 16C550 as an equivalent
part).
The pinouts for the A/V board are on page 9 of the schematics, but
here's a summary:
J607-1 - Ground
J607-2 - TX output
J607-3 - RX input
J607-4 - CTS
J607-5 - RTS
J607-6 - DTR
J607-7 - DSR
J607-8 - Key (no connection)
J607-9 - RI
J607-10 - DCD
For basic RS-232 operation, all that is needed are the first three
signal lines, and you should be able to talk to the board. If not
familiar with RS-232 interfacing, obtain a copy of the WPC-95
Schematics, as these go a long way in helping understand how the
system works.
If the chips are installed properly the operating system should detect
the board automatically and start sending audits out the port. It may
need to enable printouts in the Adjustments menu, I don't remember if
that option trips automatically.
That's all there is to it. NBA Fastbreak also used this port in a null-
modem configuration for the head-to-head gameplay (swap TX and RX
lines between games). Linked game play works like this: the first
player presses Start, and their display shows "Waiting for 2nd
player." You can play a stand-alone game by pressing both flipper
buttons, or press Start on the second machine for a linked game.
Linked games are broken down into four quarters, with a halftime. The
quarter length can be modified in the menus. The gameplay is constant,
there is not limit to the number of balls (because it's a timed game).
If a player drains the ball, a new ball is served with no penalty
(other than the time this takes). The head-to-head players select
their teams and play begins. The players work together to complete
modes. For example, player 1 might complete the two left "in the
paint" shots, and player 2 may complete the two right "in the paint"
shots, which allows that mode's multiball to start. If both players
complete all modes and reach the final (wizard) mode, they compete for
the championship ring(s). If there is a tie the game goes into an
extra overtime period.