Standard Matrix Keyboard - Kontron MOPS/386A User Manual

Kontron

Standard Matrix Keyboard

18.3
You can connect a matrix keyboard with formats up to 8*10 crossings directly to a
MOPS/386A. Pins Y0 to Y7 serve as outputs (active low), while RA0 to RA4 and RB0 to RB4
serve as inputs.
To connect a matrix keyboard, wire outputs Y0-Y7 with matrix lines and inputs RA0-RA4,
RB0-RB4 with matrix columns.
The matrix controller of the MOPS/386A has a cyclic output of a low level on the Y0 to Y7
lines. Whenever a connection (shortcut) on the matrix keyboard is made, an input line will
go low. Input lines are pulled up by 47KOhm resistors and are high as long as a connection
(shortcut) is not made by the matrix keyboard. This allows the matrix controller to
recognize a key press of the matrix keyboard by a low level on the corresponding line. The
matrix keyboard controller can only recognize a single key press; keys simultaneously
pressed (such as <CTRL><ALT><DEL>) cannot be recognized.
The matrix controller uses hardware interrupt IRQ9 to tell the MOPS/386A a key has been
pressed. A BIOS handler takes care of IRQ9. Each connection (shortcut) between a line and
a column generates an internal scan code that is transferred to the system by IRQ9. The
BIOS converts this internal scan code to a keyboard scan code using the matrix decoder
table, which is located in the onboard EEPROM.
MOPS/386A User's Guide 39 Matrix-Keyboard Interface