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tofergregg / IBM-Wheelwriter-Hack

Turning an IBM Wheelwriter into a unique printer
MIT License
98 stars 11 forks source link

Information on wheelwriter #7

Open bitcraft opened 7 years ago

bitcraft commented 7 years ago

No issue to raise. I have a WW 3 and a WW 3500 that I've been repairing slowly and I'm interested in the project you've got going. I found the following pdf that is full of good information on the overall design of the WW. The most relevant to this project information is about the data bus.

Several bus topologies and protocols were evaluated. A half-duplex multidrop line with a token-passing protocol was chosen. This satisfied the functional requirements of the product, was iexible, and though inexpensive to implement, left room for future growth. A simple two-wire interface contains the bus and token request signals to interconnect the cards and features; see Figure 8.

The token-passing protocol arbitrates communication on the bus. Only the processor having the token can initiate a bus transaction. When the machine is powered on, the function processor owns the token. Other processors request the function processor to pass the token by asserting the token request signal. When other processors are finished with the token, it is returned to the function processor.

From my own tinkering and from reading of other sources, it seems that the keyboard generates WW specific control codes and then sends them on the bus. The other devices, like the printer and floppy interface seem to just send the WW control codes, which you have begun to document. I unfortunately could not find information about them online, and it seems that manual data bus logging will be the solution.

The floppy disk controller may very well be the key to unlocking the potential of your project. By crafting a document that exposes all of the control codes, it would be possible to either sniff the data bus or simply read the contents of the floppy disk to figure out the protocol.

Just my thoughts.

https://drive.google.com/open?id=0B6n8Xp5V_REUN0g1X01DZ0JRd3M

tofergregg commented 7 years ago

Very interesting -- thanks for the added information about the bus!

If you haven't seen the video yet of type typewriter in action, check it out here: https://www.youtube.com/watch?v=0vrvDQmZcPI

I agree that a floppy controller might be helpful, as would an actual print option card. For now, I've sussed out most of the functionality that I could expect, with the exception of getting the bell to ring (but I think that is not controlled through the bus).