The first thing the keyboard does on power-up is to perform a self-test. This involves a
ROM checksum test, simple RAM test, and watchdog timer test. Whenever the keyboard is
powered up (or restarted - see below), it must not transmit anything until it has achieved
synchronization with the computer. The way it does this is by slowly clocking out 1 bits, as
described above, until it receives a handshake pulse.
If the keyboard is plugged in before power-up, the keyboard may continue this process for
several minutes as the computer struggles to boot up and get running. The keyboard
must continue clocking out ls for however long is necessary, until it receives its
handshake.
If the keyboard is plugged in after power-up, no more than eight clocks will be needed to
achieve sync. In this case, however, the computer may be in any state imaginable but
must not be adversely affected by the garbage character it will receive. Again, because it
receives a key release, the damage should be minimal. The keyboard driver must
anticipate this happening and handle it, as should any application that uses raw keycodes.
NOTE
The keyboard must not transmit a "lost sync" code after re-synchronizing due to a power-
up or restart; only after re-synchronizing due to a handshake time-out.
Once the keyboard and computer are in sync, the keyboard must inform the computer of
the results of the self-test. If the self-test failed for any reason, a "self test failed" code
(value $FC = 11111100) is transmitted (the keyboard does not wait for a handshake pulse
after sending the" self test failed" code). After this, the keyboard processor goes into a
loop in which it blinks the CAPS LOCK LED to inform the user of the failure. The blinks are
coded as bursts of one, two, three, or four blinks, approximately one burst per second:
One blink ROM checksum failure.
Two blinks RAM test failed.
Three blinks Watchdog timer test failed.
Four blinks A short exists between two row lines
or one of the seven special keys (not implemented).
If the self-test succeeds, then the keyboard will proceed to transmit any keys that are
currently down. First, it sends an "initiate power-up key stream" code (value $FD =
11111101), followed by the key codes of all depressed keys (with keyup/down set to
"down" for each key). After any keys are sent (usually there won't be any at all), a
"terminate key stream" code (value $FE = 11111110) is sent. Finally, the CAPS LOCK LED
is shut off. This marks the end of the start-up sequence, and normal processing
commences.
The usual sequence of events will therefore be: power-up; synchronize; transmit "initiate
power-up key stream" ($FD); transmit "terminate key stream2 ($FE).
- Appendix H 347 -
Summary of Contents for Amiga A1000
Page 1: ...AMIGA HARDWARE REFERENCE MANUAL 1992 Commodore Business Machines Amiga 1200 PAL...
Page 20: ...Figure 1 1 Block Diagram for the Amiga Computer Family Introduction 11...
Page 21: ...12 Introduction...
Page 72: ...Figure 3 12 A dual Playfield display Playfield Hardware 63...
Page 87: ...Figure 3 24 Horizontal Scrolling 78 playfield hardware...
Page 101: ...92 Playfield Hardware...
Page 199: ...Figure 6 9 DMA time slot allocation 190 Blitter hardware...
Page 203: ...Figure 6 13 Blitter Block Diagram 194 Blitter Hardware...
Page 229: ...220 System Control Hardware...
Page 246: ...Figure 8 8 Chinon Timing diagram cont Interface Hardware 237...
Page 265: ...256 Interface Hardware...
Page 289: ...280 Appendix A...
Page 297: ...288 Appendix B...
Page 298: ...APPENDIX C CUSTOM CHIP PIN ALLOCATION LIST NOTE Means an active low signal Appendix C 289...
Page 302: ...APPENDIX D SYSTEM MEMORY MAP Appendix D 293...
Page 343: ...334 Appendix F...
Page 351: ...342 Appendix G...
Page 361: ...352 Appendix H...
Page 367: ...358 Appendix I...
