More on the errors with the console printer (typewriter) diagnostic

USED SCOPE TO VERIFY THAT NOT READY AND BUSY ARE PRESENT

I could clearly see that when an XIO Write was issued to the typewriter, both Busy and Not Ready activated at the same time and for the appropriate duration. I traced the Not Ready signal to every location in the machine just to satisfy myself there was no issue with the DSW. 

RAN DIAGNOSTIC AGAIN, THE SAVED DSW WAS CORRECT BUT ERROR PRINTED

Indeed, after an XIO Sense Device the Accumulator (ACC) had bits 3, 4 and 5 set, which stand for Console/KB switch set to Console, typewriter busy, and typewriter not ready, respectively. This is correct. 

The diagnostic printed error E0402 which indicated that our status was not correct. The text in the documentation suggests that the busy status was wrong, but it was just poorly worded. Nor was the Not Ready status wrong - as we just verified. The error message should not have been printed. 

STEPPING THROUGH TESTING CODE, I FOUND A CONSTANT WAS INCORRECT

The code involved in this producing this error message had immediately issued an XIO Sense Device after it did an XIO Write to type a character. I saw it apply some bit manipulation then check to see that the saved DSW matched the archetype for a correct status. However, the word with the archetype status, which should have held x0C00, was instead 0x0800. This was triggering the spurious error message. 

I did a quick update of that word to the proper value, reran the diagnostic and, miracle of miracles, the error message was no longer emitted. However, if there was one corrupted value, there may be more. 

COMPARING DIAGNOSTIC ASSEMBLY LISTING AGAINST CORE FILE

I began to check the value of each word in the file I load into core to run the diagnostic, comparing it to the printed listing of the diagnostic program. This is time consuming. So far, I have found the one error word that caused the erroneous error message, but also see that the address of one routine near the end of the listing is off by two words. However, every other word so far has matched perfectly. 

As I finish the cross check, I can clean up my diagnostic program file so that it will be loaded exactly as intended by the authors at IBM and therefore should run flawlessly.