Gen cart pinout

[KanedaFr]

Sorry for this but I can't find the lastest version of the cart port pinout.

The one floating around isn't complete, I KNOW someone here put a more complete (and corrected) version (with SL1 & SR1 pins for ex)

ps: yes, I used the search button..but it can't find it

[HardWareMan]

Use it.

[KanedaFr]

ah ah! yes! I totally forgot these pics ;=)
thanks

Do you if some games use these SL1 & SR1 pins ?
I think it must only be used by the 32X no ?

[TmEE co.(TM)]

only 32X uses them.

[KanedaFr]

if you connect an external jack to these 2 pins, it will be mixed in audio ouput no ? perhaps you must be sure of the signal ? I'm not good at audio signal but I remember learning about amp....perhaps you need to be sure audio isn't already 'amped' (?) or the CXA works with any signal ?

[Chilly Willy]

only 32X uses them.

Well, SUPPOSEDLY they were used with the SVP as well... I guess SEGA was thinking that future SVP games might use the SVP for more intense audio instead of polygons. That would be closer to the original use of the DSP that makes the SVP.

[HardWareMan]

if you connect an external jack to these 2 pins, it will be mixed in audio ouput no ? perhaps you must be sure of the signal ? I'm not good at audio signal but I remember learning about amp....perhaps you need to be sure audio isn't already 'amped' (?) or the CXA works with any signal ?

The power of signal afected to SL1/SR1 must exactly same as SL2/SR2 on extension slot (for MegaCD). I guess 0.5-1 volts of amplitude will be enough and nothing goes to smoke.

[TmEE co.(TM)]

both cart and CD audip pins use same signal strenght and they are mixed straight with FM and PSG. Virtua Racing cart has the audio pins unused IIRC... I need to check again...

[Gigasoft]

Is this why my Game Genie makes strange buzzing noises in the background? Perhaps some current is leaking into one of these pins.

[eteream]

One related question (if this is totally off topic, tell me and I will delete it):

Since cart pin out has from A01 to A23, it can address 8 Megabytes. Well this is true? The upper 4MB are Sega restricted, but not hardware restricted? Or I-m missing something?

[Chilly Willy]

One related question (if this is totally off topic, tell me and I will delete it):

Since cart pin out has from A01 to A23, it can address 8 Megabytes. Well this is true? The upper 4MB are Sega restricted, but not hardware restricted? Or I-m missing something?

You're missing A0. The 68000 bus is a WORD bus. A1-23 is 16 MBytes, not 8. It's just addressed as 8 Mwords. There are byte strobes to tell the difference between "upper" and "lower" bytes on byte writes.

[eteream]

One related question (if this is totally off topic, tell me and I will delete it):

Since cart pin out has from A01 to A23, it can address 8 Megabytes. Well this is true? The upper 4MB are Sega restricted, but not hardware restricted? Or I-m missing something?

You're missing A0. The 68000 bus is a WORD bus. A1-23 is 16 MBytes, not 8. It's just addressed as 8 Mwords. There are byte strobes to tell the difference between "upper" and "lower" bytes on byte writes.

OK, It's true! memory is 16bit words.

But what I'm trying to wonder is: if the cartridge can address 16MB, why they are restricted to 4MB? From the memory map I see there is a free/reserved region between 4MB-8MB; a cartridge can realy use it to be a 8MB cart? Why the A22 & A23 wires arrive to cart pin out if a cartridge can't use it?

[HardWareMan]

But what I'm trying to wonder is: if the cartridge can address 16MB, why they are restricted to 4MB? From the memory map I see there is a free/reserved region between 4MB-8MB; a cartridge can realy use it to be a 8MB cart? Why the A22 & A23 wires arrive to cart pin out if a cartridge can't use it?

Because SegaMD has not only cartrige as hardware, that can be used.

[Chilly Willy]

But what I'm trying to wonder is: if the cartridge can address 16MB, why they are restricted to 4MB? From the memory map I see there is a free/reserved region between 4MB-8MB; a cartridge can realy use it to be a 8MB cart? Why the A22 & A23 wires arrive to cart pin out if a cartridge can't use it?

I imagine the originally, SEGA never felt carts would EVER reach 4MB. It's been that way for many companies in the computer business. Apple Mac OS not being 32 bit clean, PCs not allowing for more than 640 KB, MegaDrive carts limited to 4MB...

In the end, SEGA split up the address space so that the first 4MB were cart space, or if you had the CD going, was CD space with cart space moved to the next 4MB, and the next 2 MB was for the 32X.

You also run all sorts of lines to bus ports because you never know what you may need later on. SEGA was a little stingy on the side port, but did a bit better on the cart. Hence the 32X plugging into the cart slot instead of the side expansion port.

[eteream]

ok, so the 4MB rom space is a sega restriction, not a hardware restriction (expansion policies, if you let me say so). Then a 8MB cartridge can exist, but it will not be compatible with 32X.

... so all games are mirrored into the 4-8MB space at less... uhmm... forget it, I said nothing...