9
3.2 Interface Blocks
3.2.1 Vacuum Fluorescent Display (VFD)
This vacuum fluorescent display is a custom, stand-alone VFD module manufactured by
Futaba. It includes the VFD glass assembly, as well as all power supply and control/refresh
electronics, and a ribbon cable interconnect to the console main board.
The console VFD module interface with the Main board is by a flexible cable via connector
J6500 [sheet 13, B8] which has 5-pin as listed in following table:
Note:
(1) There is a buffer, U6802 with open collector between VFD and the CS98200. The
buffer is required to level-shift the 3.3V logic levels associated with the SPI interface to the 5V
logic levels required by the VFD module.
(2) The VFD module has built-in 1.5K Ohm pull-up resistors on the Clock, Data and Strobe
signals. There are no such pull-ups on the console Main Board; therefore, these signals will not
be measurable at connector J6500 unless the VFD is attached.
3.2.2 Button Board
The console has 6 buttons on the top leading edge. The buttons are physically located on a
small assembly which connects to the Main Board via ribbon cable into J6700 [sheet 8, D8].
Software continually monitors these buttons to detect and de-bounce a key press. Pull-down
resistors are provided to hold KEY inputs to logical 0 (ground) when no buttons are pressed.
Interconnections to the buttons are in the form of a 2x3 row/column matrix of key closures.
Each button is therefore identified by its unique row/column position.
The arrangement of buttons on the front of the console is as follows. Each circular button
represents a key closure which shorts a given KEYOUT row signal to a given KEYIN column
signal when a button is pressed. For example, ON/OFF shorts the KEYOUT0 signal to KEYIN0
when pressed:
THEORY OF OPERATION
J6500
Pin
Signal Function
1
+12V
+12V supply for the module.
2
Strobe/
Strobe for serial protocol (low when sending VFD data).
3
Ground
Power supply/signal ground.
4
Clock
Clock for serial protocol. Normally high here at the connector.
5
Data
Data for serial protocol. Normally high here at the connector.
ON/OFF
SOUR
+
ENTER
EJECT
KEYOUT2
KEYOUT1
KEYOUT0
KEYIN1
KEYIN0
VOLUME
