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Hello everyone.

I want to replace the rom on a sonic cart by an 256 kb eprom.

The address lines and data lines are easy to rewire but i have a couple of doubts.

Pin 3 of the rom is connected to WR - What to do with this signal?

Do i connect the VPP and +5V together at the eprom?

What do i do with OE pin at the eprom? Tie it to 5V? GND?

Here are the pinouts:

Thanks!

caezar wrote

Pin 3 of the rom is connected to WR - What to do with this signal?

Ignore.

Quote

Do i connect the VPP and +5V together at the eprom?

Yes.

Quote

What do i do with OE pin at the eprom? Tie it to 5V? GND?

Connect to /CE.

Philipp

Edit: Some of the SMS guys should check this, I'm just a ColecoVision developer.

The /CE line on SMS doesn't do address decoding for you, you'll have to do it yourself. So connect /CE and /M0-7 through an 'or' gate (a 74LS32 is fine) to get the /CE signal for your eprom. /OE should be connected to /RD.

I've made a dev cart by slotting a 32kB EPROM in a 128kB production cart, a few years ago, in a galaxy far, far, away. The same can be done for a 32kB game, and no mods are required.

The cart slot CE line is just the Z80 /MREQ OR-ed with the corresponding bit in IOPort 0x3E. IOPort 0x3E controls which of the BIOS, card slot (where fitted), cart slot, or expansion slot (where fitted) is active for MREQ. So as Vil says, CE will be enabled for the entire 64kByte address space, including where you don't want it to be, in the DRAM / scratchpad range.

The M0-7 line, or EXM1 is (from memory) MREQ OR-ed with A15, so it's active for the the first 32kB of the Z80 address space.

Using the cart slot CE line for the EPROM CE and the EXM1 line for the EPROM OE line work for all consoles including the MD/Genesis with the converter, EXCEPT for the early SMS, which won't even boot with the dev cart and I can't recall the exact reason why.

I hope my information rich ramblings come in handy when you're in the troubleshooting phase.

asynchronous.

Can't you connect M0-7 just to !CE line ?

TmEE wrote

Can't you connect M0-7 just to !CE line ?

M0-7 (and M8-B, MC-F) aren't affected by the slot enable bits. If it was connected to !CE directly, the cartridge ROM would be enabled when the BIOS ROM was too and you'd get a conflict.

Thanks for the replies!

PkK: It didn't work, it just stood on a black screen but thanks nevertheless.

viletim!: It works with the 74ls32.

asynchronous: Will try that. "Using the cart slot CE line for the EPROM CE and the EXM1 line for the EPROM OE line work for all consoles including the MD/Genesis with the converter, EXCEPT for the early SMS, which won't even boot with the dev cart and I can't recall the exact reason why. "

No need for the 74ls32? Just CE to CE and M0-7 to OE?

Cheers.

Hi guys,
Very sorry to bring this old topic back to life, but...

Im just trying to make a 32K cart myself, and am having similar trouble. I am trying to replace the ROM IC of a PAL The Ninja cart with a 27C256 EPROM.

So far I have just connected through all lines like so:
- address to address, data to data (obviously)
- !WR on the SMS to VPP on the EPROM
- M0-7 on the SMS to !OE on the EPROM
- !CE on the SMS to !CE/!PGM on the EPROM

This is just the way the pins worked out when I soldered the socket in place of the original chip. I imagine that !CE to !CE is okay, but what about the !WR and !M0-7 lines?

Thanks for your time everyone! Much appreciated.

Don't mind me, I am silly. Hardwiring was fine. It was my eprom programming software that was at fault. Works fine now.

Sebastian wrote

- !WR on the SMS to VPP on the EPROM

This doesn't make sense. Vpp should be connected to +5V in the cart. It's at +13V during programming. Specifications require it to be at +5V during normal operation, some EPROMS really do require +5V at Vpp during normal operation, but most will work with other values at this pin (some even allow voltages from -0.7V to VCC). I really wouldn't connect it to a signal line like !WR though. What if some EPROM really draws a significant amount of power from Vpp?

Philipp

Thanks for the information, I appreciate it. I have not had any problems thus far, but I can absolutely understand what you are saying and it is of course better to be safe than sorry. Thanks for the tip!

Author	Message
caezar Joined: 12 Sep 2006 Posts: 10	32K Eprom cart Posted: Thu Feb 07, 2008 7:00 pm
caezar Joined: 12 Sep 2006 Posts: 10	Hello everyone. I want to replace the rom on a sonic cart by an 256 kb eprom. The address lines and data lines are easy to rewire but i have a couple of doubts. Pin 3 of the rom is connected to WR - What to do with this signal? Do i connect the VPP and +5V together at the eprom? What do i do with OE pin at the eprom? Tie it to 5V? GND? Here are the pinouts: Thanks!

PkK Joined: 07 Aug 2007 Posts: 54 Location: Yach	Posted: Thu Feb 07, 2008 10:53 pm
PkK Joined: 07 Aug 2007 Posts: 54 Location: Yach	caezar wrote Pin 3 of the rom is connected to WR - What to do with this signal? Ignore. Quote Do i connect the VPP and +5V together at the eprom? Yes. Quote What do i do with OE pin at the eprom? Tie it to 5V? GND? Connect to /CE. Philipp Edit: Some of the SMS guys should check this, I'm just a ColecoVision developer.

viletim! Guest	Posted: Thu Feb 07, 2008 11:32 pm
viletim! Guest	The /CE line on SMS doesn't do address decoding for you, you'll have to do it yourself. So connect /CE and /M0-7 through an 'or' gate (a 74LS32 is fine) to get the /CE signal for your eprom. /OE should be connected to /RD.

asynchronous Joined: 14 Aug 2000 Posts: 411 Location: Adelaide, Australia	32K Eprom cart Posted: Fri Feb 08, 2008 12:01 pm
	I've made a dev cart by slotting a 32kB EPROM in a 128kB production cart, a few years ago, in a galaxy far, far, away. The same can be done for a 32kB game, and no mods are required. The cart slot CE line is just the Z80 /MREQ OR-ed with the corresponding bit in IOPort 0x3E. IOPort 0x3E controls which of the BIOS, card slot (where fitted), cart slot, or expansion slot (where fitted) is active for MREQ. So as Vil says, CE will be enabled for the entire 64kByte address space, including where you don't want it to be, in the DRAM / scratchpad range. The M0-7 line, or EXM1 is (from memory) MREQ OR-ed with A15, so it's active for the the first 32kB of the Z80 address space. Using the cart slot CE line for the EPROM CE and the EXM1 line for the EPROM OE line work for all consoles including the MD/Genesis with the converter, EXCEPT for the early SMS, which won't even boot with the dev cart and I can't recall the exact reason why. I hope my information rich ramblings come in handy when you're in the troubleshooting phase. asynchronous.

TmEE Joined: 31 Oct 2007 Posts: 458 Location: Estonia, Rapla city	Posted: Fri Feb 08, 2008 5:55 pm
	Can't you connect M0-7 just to !CE line ?

Charles MacDonald Joined: 28 Sep 1999 Posts: 1012	Posted: Fri Feb 08, 2008 7:10 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1012	TmEE wrote Can't you connect M0-7 just to !CE line ? M0-7 (and M8-B, MC-F) aren't affected by the slot enable bits. If it was connected to !CE directly, the cartridge ROM would be enabled when the BIOS ROM was too and you'd get a conflict.

caezar Joined: 12 Sep 2006 Posts: 10	Posted: Fri Feb 08, 2008 7:57 pm
caezar Joined: 12 Sep 2006 Posts: 10	Thanks for the replies! PkK: It didn't work, it just stood on a black screen but thanks nevertheless. viletim!: It works with the 74ls32. asynchronous: Will try that. "Using the cart slot CE line for the EPROM CE and the EXM1 line for the EPROM OE line work for all consoles including the MD/Genesis with the converter, EXCEPT for the early SMS, which won't even boot with the dev cart and I can't recall the exact reason why. " No need for the 74ls32? Just CE to CE and M0-7 to OE? Cheers.

Sebastian Joined: 23 Jun 2008 Posts: 17 Location: Adelaide, Australia	Posted: Mon Jun 23, 2008 9:38 am
	Hi guys, Very sorry to bring this old topic back to life, but... Im just trying to make a 32K cart myself, and am having similar trouble. I am trying to replace the ROM IC of a PAL The Ninja cart with a 27C256 EPROM. So far I have just connected through all lines like so: - address to address, data to data (obviously) - !WR on the SMS to VPP on the EPROM - M0-7 on the SMS to !OE on the EPROM - !CE on the SMS to !CE/!PGM on the EPROM This is just the way the pins worked out when I soldered the socket in place of the original chip. I imagine that !CE to !CE is okay, but what about the !WR and !M0-7 lines? Thanks for your time everyone! Much appreciated.

Sebastian Joined: 23 Jun 2008 Posts: 17 Location: Adelaide, Australia	Posted: Wed Jun 25, 2008 11:39 pm
	Don't mind me, I am silly. Hardwiring was fine. It was my eprom programming software that was at fault. Works fine now.

PkK Joined: 07 Aug 2007 Posts: 54 Location: Yach	Posted: Fri Jun 27, 2008 12:58 pm
PkK Joined: 07 Aug 2007 Posts: 54 Location: Yach	Sebastian wrote - !WR on the SMS to VPP on the EPROM This doesn't make sense. Vpp should be connected to +5V in the cart. It's at +13V during programming. Specifications require it to be at +5V during normal operation, some EPROMS really do require +5V at Vpp during normal operation, but most will work with other values at this pin (some even allow voltages from -0.7V to VCC). I really wouldn't connect it to a signal line like !WR though. What if some EPROM really draws a significant amount of power from Vpp? Philipp

Sebastian Joined: 23 Jun 2008 Posts: 17 Location: Adelaide, Australia	Posted: Sat Jun 28, 2008 10:29 pm
	Thanks for the information, I appreciate it. I have not had any problems thus far, but I can absolutely understand what you are saying and it is of course better to be safe than sorry. Thanks for the tip!

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