Keyboard button limits

  • Thread starter Thread starter FingAZ
  • Start date Start date
F

FingAZ

hey, ive noticed that whilst using my computer, games in particular that
most keyboards limit the maximum simulatenously pressed keys to three- this
is a pain in the arse- i cant press the accelerator and turn and nos all at
the same time on need for speed underground :p lol, i can press up right and
another button, but not up left and another button? why is this- and finally
the keyboard im currently using has a PS/2 connection, would i be abe to
press more key simulatenously with a USB keyboard?

FingAZ.
 
ive noticed that whilst using my computer, games
in particular that most keyboards limit the maximum
simulatenously pressed keys to three- this is a pain
and nos all at the same time on need for speed
underground :p lol, i can press up right and another
button, but not up left and another button? why is
this- and finally the keyboard im currently using
has a PS/2 connection, would i be abe to press more
key simulatenously with a USB keyboard?
Click to expand...

You should be able to find the explanation and the solution if you
Google for "key rollover" or "n-key rollover"

The problem has nothing to do with whether the keyboard is PS/2 or USB
but with the fact that the keys are laid out in a matrix of rows and
columns. The electronics scan this matrix by activating only one row
at a time and reading all the columns, and if any keys are pressed in
that row they can be pinpointed by noting the row and the column(s).
But if more than one key is held down in any given row, the electronics
can't pinpoint keys in the same column(s) but in different rows. Some
keyboards will send out character codes for those additional keys,
whether the codes are right or wrong, but other keyboards will try to
properly decode the key strokes by switching the functions of the rows
and columns, activiating one column at a time and reading all the rows,
while a few keyboards eliminate the n-key rollover problem completely
by having a diode in series with each key switch. I've seen the
latter in only one PC keyboard, but a few others had metal key switches
designed to allow installation of diodes.
 
Back
Top