|
ForumsSega Master System / Mark III / Game GearSG-1000 / SC-3000 / SF-7000 / OMV |
Home - Forums - Games - Scans - Maps - Cheats - Credits Music - Videos - Development - Hacks - Translations - Homebrew |
Author | Message |
---|---|
NeoZeed
|
Ports , memory and joy
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 |
|
|
Posted: Mon Sep 13, 1999 11:23 am |
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).
It's the same as the MSX1 VDP. Check www.msxnet.org |
|
NeoZeed
|
Posted: Tue Sep 14, 1999 6:28 am |
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 |
|
|
Posted: Tue Sep 14, 1999 10:34 am |
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.
No. |
|
Nyef
|
Posted: Tue Sep 14, 1999 1:29 pm |
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 |
|