Chapter 2: TI-83 Plus Specific Information 67
TI-83 Plus Developer Guide Third Release May 28, 2002
• Use the system key read routine, GetKey.
This method is used when the alpha and second functions on the keyboard are valid
inputs to the applications.
– Unlike polling for scan codes which returns only one value for each key on the
keyboard, this routine could possibly return up to four different values for the
same key. Depending what key modifiers, alpha and second, may have been
activated.
– See the Automatic Power Down (APD) section.
– This method will support silent link activity. Any link activity started by either
another unit or a computer will be detected by the system. If the TI GRAPH
LINK or TI Connect™ attempts transfer a variable to/from the TI-83 Plus, the
application will be shut down. See the following example.
– The pull down menu system is not controlled by this routine — the key value of
the menu will be returned but the menu will not activate.
How it works:
– Interrupts must be enabled.
– The É key flag should be reset before calling.
onInterrupt, (IY + onFlags)
– This system flag must be reset:
indicOnly, (IY + indicFlags)
If this flag is set, the interrupt handler will not scan the keyboard. This flag should
only be set when the run indicator needs to be seen and no keyboard inputs are
expected. Setting this flag will cause the interrupt service time to be shortened
and overall execution faster.
– Make a B_CALL to GetKey.
– Control remains in GetKey until a returnable key entry is pressed, the unit is
turned off, or link activity has caused the application to be put away.
– The key presses that are not returned are [ALPHA] and [2nd].
– The key code is returned in the ACC.
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