Atari 1040STE, Field Service Manual

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Note: It is possible, if pressing keys very rapidly, to leave the representation
of the key on screen in a depressed state. This does not indicate a problem
with the hardware.
The self–test checks communication between the CPU and the keyboard
microcomputer. checks RAM and ROM in the keyboard microcomputer, and scans
the keyboard for stuck keys.
3.10.1 Keyboard Error Codes
K0 Stuck key. A key closure was detected while the keyboard self–test was
executing
K1 Keyboard not responding. A command was sent to the keyboard processor
and no status was returned within the allowed time. The keyboard needs to be
replaced or the communication channel through the 6850 is not functional (see
Sec_ 3.5.1).
K2 Keyboard status error. The self–test command was sent to the keyboard, on
completion of the self–test, the keyboard sent an error status. Replace the
keyboard.
3.11 MIDI TESTS (M)
This test sends data out the MIDI port, (data loops back through the cable) and
reads from the input and verifies the data is current. This also tests the interrupt from
the 6850 through the MFP chip. The LED in the loopback cable will blink as data is
sent (not all cables have the LED).
3 .11.1 MIDI Error Codes
M0 Data not received. Trace the signal from the output of the 6850, through the
drivers, loopback cable, and receivers to the input of the 6850. Replace the
defective component as found.
M1 WriteIRead data mismatch. The data written was not the same as the data
read. Replace 6850.
M2 Input frame error. Bad 6850 or bad driver or receiver causing noisy signal.
M3 put parity error. Bad 6850 or bad driver or receiver causing noisy signal.
M4 Bad 6850 received a byte before the previous byte was read. Input data
overrun. Replace the 6850.
3.12 RS232 TESTS (S)
Note. Install Loopback Plug after power up.