User`s guide

When the pen is in reach of the tablet (up or down) this routine will
return immediately. Else it will block - fortunately, the routine checks the
keyboard strobe ($C010) too and will also return if a key is pressed, even if
the pen remains out of tablet's reach.
After the routine has returned one can get the information:
$0280 pen state:
bit 0 = 0 Pen down, bit 0 = 1 Pen up
bit 1 = Previous pen state
bit 4 = 0 Pen has been localized, its state and positions are valid.
bit 4 = 1 Pen out of reach but key pressed and then X=Y=0
$0281 Low byte of X pen position
$0282 High byte of X pen position
$0283 Low byte of Y pen position
$0284 High byte of Y pen position
X and Y have 13 bits resolution from 0 to 8191. Using my Apple Tablet, I
get values from 300 to 6350 and the bounds are not reached.
______________________________
From: Rubywand
014- My II+ keyboard acts like the CTRL key is always
pressed when it isn't. (Press 'G' get beep....press 'M'
get CR, etc.) Is there a way to fix this problem?
Are you sure that your CTRL key is not stuck? Try diddling the key. You
can, also, pull the keytop and shaft and see whether (carefully) lifting out the
small crossbar wire makes any difference. (If it does, a squirt of Radio Shack
Control Cleaner into the switch and a wipe with a cotton swab may de-gunk things
and help restore normal functioning.)
Another possible source of the problem is a KB Controller IC pin making
poor contact with the line coming from the CTRL key circuit. (Try removing and
re-socketing the KB IC.)
U1, a 7400 quad nand gate IC, could have gone bad or be making poor contact
at some pins. This could result in an 'always-pressed CTRL key' signal at pin
11.
When the CTRL key is not pressed, pins 12 and 13 of U1 (connected to the
CTRL key switch) should be at nearly 5V and pin 11 (which goes to pin 19 of the
KB Controller IC) should be at logic "0" (roughly 0V - 0.25V).
If U1 pins 12 and 13 are at 0V (or very close) when the CTRL key is not
pressed, your CTRL key switch is, probably, stuck.
If U1 pins 12 and 13 are at/near 5V and pin 11 is not near 0V, U1 is
probably bad or making poor contact at some pins.