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View Full Version : MicroSPrite S100 bouard with TMS9918A chip and 4116's. :) help?



waltermixxx
August 24th, 2016, 03:55 PM
Hi there, I'm wondering what is the best way to test this board...
I have it installed on my "JAIR8080" which can be best discribed as a
Modern day Imsai based on Josh Bensadon's 8080 board, and Don Caprio's
Mini Front Panel. The serial ports are built in (8250 chips x 2) and so is an
sd card interface which acts as 4 drives for cpm.

The MicroSprite has two sets of Jumpers one for the Port address and the other for the interrupt.

I currently have the board set to use Ports 80 and 81.

when i power on the system, i do get a black raster on my lcd monitor on the video output,
so it looks like it's generating video. however right off the bat it's black. I was wondering,
if it should be black or if it should maybe have some random characters or something up on the display.

The RAM chips are a bit warm, but not hot, and so is the TMS9918. I'm sure I have 4116's somewhere i can try
replacing the ram with. But nothing currently has me thinking there may be an issue... Wondering about
the dreaded "black screen" Ti99/4a can get?

i dont have the schematic, and there appears to be no reference to it on the internet, except perhaps my own.

I have the VPD programming guide, and data sheets for the TMS9918, but wondering if I should be seeing anything
on the screen at power up or reset? is there a quick set of data i could send it to perhaps generate a red background,
and blue border?

I know i use the two ports to communicate with it, just confused somewhat on the best way to initialize it.

in MBASIC i can use OUT xxx, yyy ( Port number, Data )
I can also use A=INP(xxx) where xxx is the port number.


here are pictures of the board:

32781
32782
32783

I would love to be able to draw to this board...

:)

gertk
August 27th, 2016, 08:18 AM
From the datasheet: Chapter 2.1.7 VDP initialization

After reset the display is blanked. (blank bit in VDP register 1 is reset to 0)

ftp://ftp.whtech.com/datasheets%20and%20manuals/Datasheets%20-%20TI/TMS9918.pdf

waltermixxx
September 1st, 2016, 02:07 PM
Thank you. :)

Yes thats a very good resource. I appreciate the link.

I have been reading it, and managed to get A picture on the display ( ok just some random crap, and a colour back ground that i can change to one of the 15 colours. :).

I appreciate your reply :)

I also posted this in the S100 section and posted pictures there. :)

Cheers. :)