Saturday, June 11, 2022

Possible defects in the IBM 1130 based on some hand entered code

ENTERED CODE TO TEST OUT THE REMAINING KEYBOARD CONTROLLER FUNCTIONS

There were three steps left in my full test of the keyboard device controller functionality. I wanted to verify that each and every key produces the proper hollerith code, check that an XIO Sense Device with Reset will turn off the interrupt request trigger, and test that a BOSC (Branch Conditional with bit 9 on) will turn off the interrupt level.

I BELIEVE I DISCOVERED SOME ERRONEOUS BEHAVIOR

I could NOT get a BOSC to turn off the interrupt level. Not sure if this is due to repeated triggering from the device controller or a flaw in the execution of BOSC. There were also some oddities with processing of long (doubleword) instructions that I saw.

INVESTIGATION PLAN

I can run the machine with interrupts blocked, thus it won't ever go into the interrupt routine. That will allow me easier coding for a loop to XIO Control (select the keyboard), wait, then XIO Read to view the hollerith code returned.

It will also give me easy visibility to the function of XIO Sense Device with Reset, in that I should see the request for an interrupt go away so that when I flip off the interrupt block switch, it does not jump there. 

I will hand step through some long format instructions to carefully exam their execution. The problems could have been coding errors on my part, but I will look closely to catch any defects that might exist.

No comments:

Post a Comment