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Hi all,

I've start a sg1000 emu but i can figure out some spec of the TMS9918. It's about the VDP register ...

For example, i follow Zoop docs, i read that for obtaining the Tile starting address (reg4) i must (in mode 1) anded the value of the reg4 with 0x3f (so 6 bits) but when i look in the Tms pdf it says that only the first 3 bits are useful , why this mask of 6 bits (0x3f) ?? What's the technical reason for this ??

Thanks in advance

NeoZeed

Quote

> I've start a sg1000 emu but i can figure out some spec of the TMS9918. It's about the VDP register ...
> For example, i follow Zoop docs, i read that for obtaining the Tile starting address (reg4) i must (in mode 1) anded the value of the reg4 with 0x3f (so 6 bits) but when i look in the Tms pdf it says that only the first 3 bits are useful , why this mask of 6 bits (0x3f) ?? What's the technical reason for this ??

In don't have the answers handy, not even sure which is the good mask to use.
But in any cases, I suggest not trusting my doc at all. It is a draft I made sometime ago and I believe it's full of mistake.

Quote

> Hi all,

> I've start a sg1000 emu but i can figure out some spec of the TMS9918. It's about the VDP register ...

> For example, i follow Zoop docs, i read that for obtaining the Tile starting address (reg4) i must (in mode 1) anded the value of the reg4 with 0x3f (so 6 bits) but when i look in the Tms pdf it says that only the first 3 bits are useful , why this mask of 6 bits (0x3f) ?? What's the technical reason for this ??

>

If you want a fully working TMS9918 core check out Marat's old one which is included in his emulib i believe. If you want these files i think i have them still..

ATani

Quote

> In don't have the answers handy, not even sure which is the good mask to use.
> But in any cases, I suggest not trusting my doc at all. It is a draft I made sometime ago and I believe it's full of mistake.

In fact, i follow the Marat's code (emulib) with yours spec but i try to understand all what i read and there's some black point,... but i'll try to admit without understanding (damn..)

Thanks you all.

Author	Message
NeoZeed Guest	SG1000 VDP Posted: Sun Apr 23, 2000 4:44 pm
NeoZeed Guest	Hi all, I've start a sg1000 emu but i can figure out some spec of the TMS9918. It's about the VDP register ... For example, i follow Zoop docs, i read that for obtaining the Tile starting address (reg4) i must (in mode 1) anded the value of the reg4 with 0x3f (so 6 bits) but when i look in the Tms pdf it says that only the first 3 bits are useful , why this mask of 6 bits (0x3f) ?? What's the technical reason for this ?? Thanks in advance NeoZeed

Zoop Joined: 24 Jun 1999 Posts: 1732 Location: Paris, France	Posted: Sun Apr 23, 2000 5:06 pm
	Quote > I've start a sg1000 emu but i can figure out some spec of the TMS9918. It's about the VDP register ... > For example, i follow Zoop docs, i read that for obtaining the Tile starting address (reg4) i must (in mode 1) anded the value of the reg4 with 0x3f (so 6 bits) but when i look in the Tms pdf it says that only the first 3 bits are useful , why this mask of 6 bits (0x3f) ?? What's the technical reason for this ?? In don't have the answers handy, not even sure which is the good mask to use. But in any cases, I suggest not trusting my doc at all. It is a draft I made sometime ago and I believe it's full of mistake.

ATani Guest	Posted: Sun Apr 23, 2000 5:46 pm
ATani Guest	Quote > Hi all, > I've start a sg1000 emu but i can figure out some spec of the TMS9918. It's about the VDP register ... > For example, i follow Zoop docs, i read that for obtaining the Tile starting address (reg4) i must (in mode 1) anded the value of the reg4 with 0x3f (so 6 bits) but when i look in the Tms pdf it says that only the first 3 bits are useful , why this mask of 6 bits (0x3f) ?? What's the technical reason for this ?? > If you want a fully working TMS9918 core check out Marat's old one which is included in his emulib i believe. If you want these files i think i have them still.. ATani

NeoZeed Guest	Posted: Mon Apr 24, 2000 9:37 am
NeoZeed Guest	Quote > In don't have the answers handy, not even sure which is the good mask to use. > But in any cases, I suggest not trusting my doc at all. It is a draft I made sometime ago and I believe it's full of mistake. In fact, i follow the Marat's code (emulib) with yours spec but i try to understand all what i read and there's some black point,... but i'll try to admit without understanding (damn..) Thanks you all.

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