More bench testing of 1627 controller card

COMPLEX BENCH TESTING SETUP SEEMS TO BE WORKING

The SLT breakout box provides each signal on a banana plug jack. Where it gets cumbersome is when I have to connect to a wire going into a breadboard or some other device. I have some banana cables with alligator clips but mostly they are male to male types. As you can see below, it gets messy interfacing many input and output signals from an SLT card.

I ordered quite a few banana plugs that I can solder to wire segments suitable to inserting in a breadboard or an Arduino type device. That will make this process much easier the next time around. I made up enough to rewire the testbench and clean things up. 

I put the new Arduino Uno into the testing setup and now see the XIO Write signal asserted properly. This gives my card the three signals it needs to accept a write request from the 1130 - XIO Write, Area 5 and T6. When those occur, the state machine proceeds through to generate the request for an interrupt at the completion of the commanded plotter movement. 

CONTINUING TESTING, USING SCOPE TO OBSERVE OUTPUTS

I used a four channel scope to capture sets of output signals from the card. The signals produced to drive the plotter are inverted logic 12V levels, the signals to the 1130 are inverted 3V levels, and some of them required pull-up resistors since the 1130 normally provides the pull-up. 

Activating the DC Reset line sets the board in its idle configuration - all six plotter outputs would be de-asserted to 12V levels, the four outputs to the 1130 would be de-asserted at 3V levels, and internally it should have the busy state turned off. I checked this first. Works perfectly. 

Sense while idle but no -24 power

Without plotter power connected, the DSW should show that the plotter is not ready. This occurred - bit 15 of the DSW is 1. 

Sense while idle with -24 power

The sense should show the plotter ready but not busy and no operation complete. Interrupt level 3 will remain high. The DSW has all bits off, which is correct, and no operation complete or interrupt request.

Trigger write requesting to move the pen up

The signal to the plotter should drop low for an appropriate time. After an additional interval the interrupt level 3 signal will drop low. For the model 1, the time for a plotter signal to cause this operation is 1.9 milliseconds, followed by a second 1.9 ms interval, all of which has the plotter indicating busy by putting a 1 in bit 14 of the DSW if a Sense Device is executed during this time. At the end of the 3.8 ms, the interrupt request for level 3 becomes 0 (inverted logic levels) and a DSW will have bit 0 turned on from this point onward. 

A 1627 model 2 will use 2.9 milliseconds for the duration of the command to the plotter and an additional 2.9 ms of busy time before triggering the interrupt request. I checked by temporarily placing a jumper on the card and verified the two durations  were correct for both model 1 and model 2. 

Sense then sense with reset issued

The sense should show operation complete (DSW bit 0) but not busy (DSW bit 14 off) and ready for further operations (DSW bit 15 off). It should only turn off the operation complete status (DSW bit 0) and interrupt level 3 will go high when the Sense with reset bit 15 is issued, not with a regular Sense Device. This worked exactly as intended. 

Trigger write requesting raising pen off paper

The raise command should do the same things as the prior write but the timing will be longer as is appropriate for raising and lowering the pen. The command to the plotter is held for 50 milliseconds, then a second interval of 50 milliseconds follows that; during the entire 100 ms, the plotter is shown as busy (by a 1 in DSW bit 14).  This is the same for either model of the plotter. I verified that this works correctly. 

Trigger write with both left pen movement and raising it off the paper

Requesting both types of movements should drop the 'left' command after 1.9 or 2.9 ms but maintain 'raise' for a full 50ms. The plotter is busy through the entire 100 ms interval. The interrupt level and operation complete only occur after the raise is complete. This was verified on the bench. 

Trigger above dual write test while -24 power is off

If -24V is off, no movement is commanded of the plotter but the interrupt request is immediately issued and the operation complete (DSW bit 0 set) is shown too. Initially I blipped the command signals to the plotter for 80 nanoseconds before my logic determined it should give an immediate operation completion. 

I decided to avoid this, thus recoding a bit of the FPGA state machine. It now proceeds immediately to completion status without toggling any of the signal lines to the plotter. 

RESULTS OF THE TESTING

The bench testing setup was fragile, but with some work it became reliable enough to perform all the tests I wanted. I had simulated all of this in Vivado previously but it is good to see the actual behavior match what I designed and expected. 

The board was inserted into the IBM 1130 in order to be put through its paces being driven by software commands and interacting with the 1130's interrupt and sense device mechanisms. I began building a connector to fit into slot N5 of gate A, compartment C1 of the 1130, with wiring that will deliver the six command signals to the plotter (pen left, pen right, drum up, drum down, raise pen and lower pen) as well has carry the -24V from the plotter that indicates to the controller that the plotter is ready to receive commands. 

I found the correct parts on Mouser to build SLT sockets to connect wiring to the backplane of the 1130. I started wiring the connector and cable before I ran out of steam today.