Forums

Sega Master System / Mark III / Game Gear
SG-1000 / SC-3000 / SF-7000 / OMV
Home - Forums - Games - Scans - Maps - Cheats - Credits
Music - Videos - Development - Hacks - Translations - Homebrew

View topic - Ports , memory and joy

Reply to topic
Author Message
NeoZeed
  • Guest
Reply with quote
Ports , memory and joy
Post Posted: Mon Sep 13, 1999 10:43 am
Hello there,

Ok, i've finally set up the mz80 cpu core (from neil bradley). And now i'll code all about the memory and the ports. But after reading the doc from zoop about the SG1000, i've a question.

The sg1000 memory map is as follow (source from zoop) :

0x0000 ------------------------------------------------
ROM (read-only)
0x8000 ------------------------------------------------
Unused on SG-1000
0xA000 ------------------------------------------------
RAM (read/write)
0xC000 ------------------------------------------------
Mirror of RAM (read/write)
0xFFFF ------------------------------------------------

and the joystick port is at 0xDC so where are locate the ports, it'seems that this adress is located in the rom section (for me). Is there a difference between Ports and memory ?

How could i write to the port when i've detect that the user has move the joy ? If i do Z80MEMORY[0xdc]= 0x1 (for the user put down) is it right ?

Does anyone has informations (others that the zoop'ones) about the sg1000 vdp ?

Tia

NeoZeed

 
  • Joined: 24 Jun 1999
  • Posts: 1732
  • Location: Paris, France
Reply with quote
Post Posted: Mon Sep 13, 1999 11:23 am
Quote
> and the joystick port is at 0xDC so where are locate the ports, it'seems that this adress is located in the rom section (for me). Is there a difference between Ports and memory ?
> How could i write to the port when i've detect that the user has move the joy ? If i do Z80MEMORY[0xdc]= 0x1 (for the user put down) is it right ?

Input/output ports are separate from the main memory on Z80 based system.
Basically, a port is a special location. On the MZ80 code, you have to define a table with your port handlers.
The programs interact with ports with the OUTA and INA opcodes.
(OUTA= write A to port, INA=read port and store result in A).

Quote
> Does anyone has informations (others that the zoop'ones) about the sg1000 vdp ?

It's the same as the MSX1 VDP.
Check www.msxnet.org
  View user's profile Send private message Visit poster's website
NeoZeed
  • Guest
Reply with quote
Post Posted: Tue Sep 14, 1999 6:28 am

Quote
> > Does anyone has informations (others that the zoop'ones) about the sg1000 vdp ?

> It's the same as the MSX1 VDP.
> Check www.msxnet.org

Ok, i've look to this and it seems there's some difference between the the TMS9918A (msx) and the TMS9918. So i suppose that the vdp is a TMS9918. I've also look to the marat'tms9918 code (from his emulib), do you use these vdp code for meka ?

Tia

NeoZeed
 
  • Joined: 24 Jun 1999
  • Posts: 1732
  • Location: Paris, France
Reply with quote
Post Posted: Tue Sep 14, 1999 10:34 am
Quote
> Ok, i've look to this and it seems there's some difference between the the TMS9918A (msx) and the TMS9918. So i suppose that the vdp is a TMS9918.

I don't know the exact name, but most SG-1000 games uses the video mode which is split in 3 three sets (one for the top, one for the middle and one for the bottom of screen) and a few other games use the same mode but with only 1 tile set.

Quote
> I've also look to the marat'tms9918 code (from his emulib), do you use these vdp code for meka ?

No.
  View user's profile Send private message Visit poster's website
Nyef
  • Guest
Reply with quote
Post Posted: Tue Sep 14, 1999 1:29 pm
Quote
> Ok, i've look to this and it seems there's some difference between the the TMS9918A (msx) and the TMS9918. So i suppose that the vdp is a TMS9918.

Not likely. The 'A' suffix was either ignored in one case or is indicative of a special property of the chip (operation speed or industrial hardening, for example). See the Z80 vs. the Z80A for more details of silly stuff like this.

Next you'll be telling us that the ColecoVision uses another completely different VDP from the TI99/4A, the MSX, and the SG1000, even though they all have the same part number.

Chances are that the SG1000 docs you are using simply describe the most commonly used mode for SG1000 games.

--Nyef
 
Reply to topic



Back to the top of this page

Back to SMS Power!