STAR*TECH
Journal
September 1996
SEGA PINBALL TECHNICAL SUPPORT
7 SEGMENT DISPLAY OPERATION
TEAM SEGA
Joe Blackwell, Eric Winston, Ted Kilpin,Jay Alfer
Sega Pinball, Melrose Park, Illinois
7-Segment
ALPHANUMERIC
14-Segment
& 7-
SEGMENT DISPLAY OP-
ERATION
We receive calls now
and then asking the
following questions ...
"Which segment is
"D" or "F" etc ... ?"
"Which side of the
glass does Pin- I start
on ... ?" "How does this
thing work!?" Since
everyone in our Tech
Support Dept. has worked for an
operator or distributor at one
time or another and we have
asked the very same questions .. .in
response, we have dug up our
scratch notes on the back pages
of old manuals Qust like you guys
have done) and put together this
comprehensive overview of a 16-
Digit Alphanumeric Display, and
also individual digits describing
the segment names for a 7-Seg-
ment & 14 Segment Digit. What
a great page to hang on your wall
for quick reference! Don't worry
though, next issue we will con-
tinue our White Star Board Sys-
tem Theory of Operation.
How IT WoRKS
In order to display a character of
data on the display glass, two
things must happen: • The cor-
rect segment drive information
must be applied to the display
glass, AND • A Digit Strobe or
Select Drive Signal must appear
at the correct Digit Drive posi-
tion. The segments of each dis-
play digit correspond electrically
to CATHODES; that
is, they require a
NEGATIVE drive
voltage for operation,
and each display digit
connection (which are
CLEAR conductors
deposited on the TOP
glass of the display
sandwich) can be
thought of as the AN-
O DE, driven by a
POSITIVE drive sig-
nal. These drive voltages are typi-
cally on the order of +90v DC
for the digits (Anodes) and -IO0v
DC for segments (Cathodes).
From a digital logic standpoint,
the game CPU generates the seg-
ment information on a P ARAL-
LEL basis, meaning that all seg-
ment information is output AT
ONCE to the display drivers, and
digit information appears in a
SERIAL or SEQUENTIAL for-
mat; such that ONLY ONE digit
select at a time is EVER active.
For example, to display the num-
ber "1" at digit location 2, seg-
ments "B" and "C" (Pin- 4 and
Pin-12) are turned ON (they go
to -IO0v DC) with all other seg-
ments turned OFF, and digit
drive 2 (Pin-11 and/or Pin-13)
goes to +90v DC.