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F18A MK2

F18A VDP 9918A

378 replies to this topic

#376 JCCyC OFFLINE  

JCCyC

    Space Invader

  • 32 posts

Posted Mon Apr 22, 2019 4:02 PM

I have a Japanese MSX computer with a busted VDP to be a loving home for a Mk2. It's with a friend who fixes retro computers, he's having some difficulty procuring the VDP. I'll have to check the pinout, I think there are variants with different pinouts, is that right?



#377 patrickmcmichael OFFLINE  

patrickmcmichael

    Star Raider

  • 51 posts

Posted Wed Apr 24, 2019 5:28 PM

Any good word on the F18A MK2? Having gotten back into the TI-99/4A after the original F18A was beyond run, and having seen the tentative MK2 specs and features, I am super excited!



#378 seastalker OFFLINE  

seastalker

    Chopper Commander

  • 210 posts

Posted Wed May 15, 2019 7:11 PM

I just learned of this project for the TI99 and hope to learn more... standing by on availability



#379 matthew180 OFFLINE  

matthew180

    River Patroller

  • Topic Starter
  • 2,629 posts
  • Location:Castaic, California

Posted Thu May 16, 2019 4:02 PM

Bulk reply, sorry for being impersonal:

 

The MK2 is still my priority hobby project and I am giving it as much time as I can spare.  It will happen, but usually never as fast as I, or anyone else, would like.  I hope to ramp it up soon, and I will be posting here for sure when I have progress to report.  I know my website has not been updated in a long time either, and my contact form and emails are backing up too.  So if you have sent me a message recently, please know that I have received it and I will get back to you.

 

 

I have a Japanese MSX computer with a busted VDP to be a loving home for a Mk2. It's with a friend who fixes retro computers, he's having some difficulty procuring the VDP. I'll have to check the pinout, I think there are variants with different pinouts, is that right?

 

There are a few variations of the 9918A with the main differences being in the video and oscillator outputs.  The F18A supports every variation that I am aware of.  Due to the total lack of F18A documentation (also on my TODO list), here are the variation details:

   -- User header.  Pull-up in the FPGA, a jumper in place will pull to ground.
   --
   --  User Jumper          |  On  | Off
   -- --------------------------------------
   --  1 Sprite max default |  32  | 4
   --  2 Scan lines         |  No  | Yes
   --  3 CPUCLK pin         | P38  | P37
   --  4 CPUCLK en          | HI-Z | CPUCLK

   -- USR3 CPUCLK pin.  Provides support for the 9128/9129 that output CPUCLK on pin37.
   -- USR3 and USR4 - CPUCLK pin and CPUCLK Enable.
   --        _________
   -- RAS  =|1   U  40|= XTAL1    9918A   9928A/29A  9118   9128/29 F18A
   -- CAS  =|2      39|= XTAL2   ======== ========= ======= ======= ====
   -- AD7  =|3      38|= ....... CPUCLK   R-Y       CPUCLK  R-Y     HI-Z / CPUCLK
   -- AD6  =|4      37|= ....... GROMCLK  GROMCLK   NC      CPUCLK  GROMCLK / CPUCLK
   -- AD5  =|5      36|= ....... COMVID   Y         COMVID  Y       NC
   -- AD4  =|6      35|= ....... EXTVDP   B-Y       EXTVDP  B-Y     NC
   --

   -- Basically:
   --             USR3 USR4
   -- TI-99/4A     on   on    -- The 99/4A does not use the CPUCLK, but this is NOT the default of the 9918A
   -- 9928/29      on   on    -- CPUCLK on pin38 disabled so it does not cram 3.5MHz into the R-Y circuit
   -- 9918A/9118   on  off    -- CPUCLK output, GROMCLK output (pin37 is not connected on the 9118)
   -- 9128/29     off   on    -- CPUCLK on pin37 enabled, CPUCLK output on pin38 disabled
   -- not used    off  off    -- CPUCLK output on both pin37 and pin38

Basically the differences in the 9918A family are pins 35, 36, 37, and 38.  If you have or know of some other variation, please let me know.  The MSX1 spec used the 9918A for NTSC and 9929 for PAL (I don't think the 9928 was used, but it could have been in some MSX1 systems).  The MSX2 uses the 9938, which the F18A does not replace (although the MK2 might develop that capability in the future (do not read into that, do not hold your breath)).







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