Digitek screenmaster 80 card

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Digitek screenmaster 80 card

Hi everyone, has anyone ever come across the Digitek Screenmaster 80 column card for the Apple II ?

if so do you have any documentation etc ?

Cheers

Andy

 

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Can you post some pics?  Many

Can you post some pics?  Many 80 column cards from lesser known brands were clones of the Videx Videoterm.

 

 

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Here is about the best I have

Here is about the best I have found online so far...  Look at the advert on page 128.

 

https://worldradiohistory.com/UK/Practical-Computing/80s/Practical-Computing-1983-03-S-OCR-IA.pdf

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Interesting card. Have you

Interesting card.

 

Have you got one?  The mied text/graphics mode is neat, but I wonder just how much software would have been written for this.

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I do have one and after some

Package iconappleii80eprom.bin_.zip

 

I do have one and after some research found it works in a similar way to the Vision-80 (though the design is different)

 

https://archive.org/details/TheVision80VideoCardOwnersManualAppleII

 

in terms of how the CTRL key codes work to operate the board (switch modes etc). There are some differences when I look at the ROM code (attached) command key table (CTRL Z followed by a letter) with additional functionality such as Insert line and Delete Line. However despite having the lower case key mod in place I cannot get it display lower case charatcers. CTRL A is not in the ROM code and just pressing Shift (acting as a shift lock in the same way as the Vision-80 card) also does nothing. I could not find any reference to PB2 also so no idea of how it detects the shift key. Try as I might I cannot find how to get Lower Case chaarcters as of yet (will keep trying).

 

The dual cable running along the top of the board I believe is for a Shift Lock LED. One of the cables is permenantely at 5volts and other goes to the output 2Q of a 74ls74 IC.

 

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AndyG001 wrote:appleii80eprom
AndyG001 wrote:

Package iconappleii80eprom.bin_.zip

 

I do have one and after some research found it works in a similar way to the Vision-80 (t

 

 

Good find.  The Vision 80 and this one vary a little in design, the Vision 80 uses 4x 2114 1kx4 DRAMs and this one uses a 6116 2kx8 SRAM.  But both use the 6845 CRTC and a 2732 for the ROM and CHARGEN functions.  Actually that's all a pretty common parts list for a lot of Apple II 80 column cards.  Videx Videoterm and the ALS SmartTerm use similar arrangements.  Some cards use the Hitachi clones of the 6845 and some use different size EPROMs, but most of the functional differences and compatibilites between them are in the EROM code and the charsets.  They all vary in the interfacing logic of how things hook up to the Apple II bus, but they're all doing basically the same things.

 

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I am struggling with

I am struggling with displying lower case - the character rom has lower case characters but cannot find the key sequence which is not like other 80 col cards.

Ctrl A or Shift don't work.... switching character roms is not clear also as this is another difference between the Vision-80 and Digitek board ... 

Is there anyone familiar with programming cards who can take a look through the rom dump I posted ?

Cheers

Andy

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What software are you trying

What software are you trying to enter lower case into?  Try word processing software.

I'm assuming you are entering 80 columns by PR#3?

If I remember right the Applesoft BASIC interpreter doesn't allow lower case input until the //e, and certainly doesn't support the "one wire" type shift key mod.  You might get 80 columns if you have a lower case capable keyboard like one of the 3rd party ones or on a later ][+ with the separate encoder card if you install a switch into the solder pads.

 

 

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Yes I am in 80 column mode.

Yes I am in 80 column mode. When you say "install a switch into the solder pads" can you provide me with more information ?

The Keyboard does have a separate encode board. If I look at the VIDEX rom chip it checks for PB2 ($C063) - if the shift key is down with the single wire mod. The code for my boards ROM has no reference to $c063 at all. It does use  $c066 and $c067, paddle 2 and 3 (BIT $C066 for example) but not sure why.  

 

Cheers

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AndyG001 wrote:Yes I am in 80
AndyG001 wrote:

Yes I am in 80 column mode. When you say "install a switch into the solder pads" can you provide me with more information ?

The Keyboard does have a separate encode board. If I look at the VIDEX rom chip it checks for PB2 ($C063) - if the shift key is down with the single wire mod. The code for my boards ROM has no reference to $c063 at all. It does use  $c066 and $c06

 

Your pic of your card, right behind the K in Digitek, you can see your encoder board.  Right there is a spot for a switch outlined.  If you install a switch there (or as I've done in the past, on enough wire to allow it to go out the back of the machine), that works like a caps-lock.  You can switch it into a mode where you can enter lower case.

 

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Digitek screenmaster 80 card

This card is a slightly later re-do of the Australian Vision-80 card using static ram and a 6845 CRT controller.  The hardware and software for both cards was done by my friend Ken Thompson. His partner at the time was Harry Harper (Zofarry Enterprised Pty Ltd).  Ken developed the Vision-80 card in Sydney,  I was the proud owner of the wire wrapped prototype for many years, but that is another story.

 

Between 1980 and 1982 I moved to London to continue training in my profession, I had contact with Digitek over a pre-boot disc for Visicalc, casually mentioning that Ken had done a number of improvements  (too late) after the Vision-80 was in production.  He had managed to triple the scrolling speed (text) by allowing the 6502 to access the RAM simultaneously whilst the 6845 was reading the RAM.  Ken was invited to London by Digitek and the Screenmaster 80 was born.

 

If you scroll 80 column text, there are tiny glitches of black, only visible over white text, caused by the 6502 reading the RAM whilst the 6845 reads it.  A hack on the Vision-80 gave a similar speed increase, but the glitches were white causing snow on the screen during a scroll. With a bit of electronic trickery on the Screenmaster 80, Ken inverted the glitches to black so that it was hardly visible during scrolling.

From memory, the address switches including RAM addresses and blanking ports were identical to the Vision 80. Vale Ken.

Laurie (Ex Pynwon Computer Services)

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Thankyou for the information.

Hi Laurie

 

Thankyou for the information..... I have come to the conclusion I do need the pre boot disc but this has not been published online. Would you or Ken have something lying around in a draw or box that can help me ?

 

The dip switches do visually change the character spacing but without more info I cannot drill down further. I have disassembled the rom but not being an Apple II guru I am having difficulties following the code including trapping the ctrl z command and also lowercase/character rom switching.

 

thanks again for that enlightening information.

andy

 

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DIP Switches

I have figured out the DIP switches by tracing tracks 

 

DIP 

1:- linked to dispen of the CRTC 6845 and whilst I didn't notice any effect when switching think this maybe related to the fast scrolling mode

2:- Linked to  the CRTC 6845 - this allows overlay of text on the graphics screen

3:- Inverse flag

4:- Alternative character ROM select

A pre-boot disc is necessary for VisiCalc and Writer but not sure what the contents of the discs are and how to recreate....

 

It seems this design uses dip switches to select options that were under software control on the Vision-80

Looking at the ROM code there are references to $c066 and $c067 which are x/y on PDL2 ... after it looks for a keypress at  $c000... haven't figured that out yet

 

Still hoping with fingers crossed someone comes across more documentation or software to complete the setup

 

Cheers

Andy

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Keyboard modification
Figured out the keyboard modification to switch between upper and lower case...very different to Videx and also Vision-80

 

You need a dip socket (16-pin) soldered on top of a dip header and cut pins8 and 9 on the socket off.Then two wires are connected to the upper pins 9 & 8 on the header the other ends go to pin 24 (shift) and pin 3 (ctrl) respectively on the keyboard encoder.

 

The dip adapter socket then goes into H13 which is the 558 timer with the 558 IC plugging into DIP socket.

 

This effectively disables PDL2 and PDL3 of the game port ($c066 and $c067) replacing the outputs with that from the keyboard encoder.

 

To go to lower case press the ctrl and shift key simultaneously, the Apple beeps and changes case (connecting a LED to the twin wire ... it's off for lower case and on for upper case)..press the two keys again to return to upper case.

 

Dip 1 is defo fast (off) or smooth (on) scrolling ....

 

Now how to find the pre boot disks.....

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