IBM 1130 typewriter (console printer) repair and adjustment - part 10

USING SCOPE TO VERIFY BUSY CONDITION FROM TYPEWRITER

I could clearly see the -Twr CB Response signal drop during the typing of each character, although the console printer diagnostic as reporting that the DSW did not show the typewriter busy when it was sensed immediately after an XIO Write was executed. 

There could be a failure in the controller logic inside the 1130 system that is failing to indicate the busy condition. This is set when the XIO Write instruction is completing and cleared by the -Twr CB Response signal having gone low for a while and then returning to high. When the signal returns to high, besides turning off the busy signal it also requests an interrupt on IL4, presenting Operation Complete status.  

HAND CODE TO ISSUE XIO WRITE AND XIO SENSE DSW IMMEDIATELY AFTER

I set up the machine so that when the interrupt arrives on IL4 when the typing completes, the machine simply waits. Then, the code that fires off the character typing has a sense DSW immediately, stores it in a chosen memory location and at the end waits.

I could see that the Accumulator, as well as the chosen memory location, contained x3C00 which is not correct for what should be happening. This is why the diagnostic complained. I was suspicious because the value happened to match the character I asked to type - x3C is an A - so I altered the character I was typing to J (x7C) and that value was now returned for the  Sense DSW.

This should NOT happen.  This is not a typewriter issue, so I will blog about this under a new title and once it is resolved I can go back to documenting the console printer repair and adjustment.