EEPROM (or flash) replacement for Oric-1 ROM?

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tingo
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EEPROM (or flash) replacement for Oric-1 ROM?

Post by tingo » Sun Oct 18, 2009 7:39 pm

The ROM chip in my Oric-1 is a 23128 (a PROM, actually). I can replace it with a 27128 EPROM (why? to run an updated version of the ROM of course).
But before I do that - are there any EEPROM (or even flash) chips available that are pin- and voltage compatible with the 27128 / 23128?

EEPROM chips are so much easier to work with, no need for that time-consuming UV erase process...
Torfinn

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carlsson
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Post by carlsson » Mon Oct 19, 2009 10:14 am

I'm not too familiar with those, but I believe the smallest Flash you can get would be a 29F256, i.e. 32K device in a 28-pin DIP. There seems to exist a 29C256 too, but the datasheets only mention TSOP and PLCC packages although some places are selling them in DIP packages too.

Code: Select all

       29F256                   27128
     __________               __________
    |    u     |             |    u     |
  W | 1     28 | Vcc     Vpp | 1     28 | Vcc
A12 | 2     27 | A14     A12 | 2     27 | /PGM
 A7 | 3     26 | A13      A7 | 3     26 | A13
 A6 | 4     25 | A8       A6 | 4     25 | A8
 A5 | 5     24 | A9       A5 | 5     24 | A9
 A4 | 6     23 | A11      A4 | 6     23 | A11
 A3 | 7     22 | /OE      A3 | 7     22 | /OE
 A2 | 8     21 | A10      A2 | 8     21 | A10
 A1 | 9     20 | /CE      A1 | 9     20 | /CE
 A0 | 10    19 | D7       A0 | 10    19 | D7
 D0 | 11    18 | D6       D0 | 11    18 | D6
 D1 | 12    17 | D5       D1 | 12    17 | D5
 D2 | 13    16 | D4       D2 | 13    16 | D4
GND | 14    15 | D3      GND | 14    15 | D3
    |__________|             |__________|

  W = Write Enable ( == Vpp ??)
/OE = Output Enable
/CE = Chip Enable
Vcc = 5V power
I haven't looked up the exact pinout of a 23128, but assuming at least pin 27 has no function, it may work as a replacement? Somebody else can comment, perhaps add more options. You may need to flash it with an image containing the ROM twice since it is 32 kB but the Oric will only expect a 16K device.
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Post by Silicebit. » Mon Oct 19, 2009 11:07 am

Hi tingo!.

I think you can use a 28256/28C256 EEPROM or 29F256 FLASH EPROM, datasheet for 28C256 EEPROM here:

http://www.datasheetcatalog.com/datashe ... C256.shtml

I've my Atmos with an EPROM programmed with a Pascal Leclerc's version of Oric Atmos ROM and works fine.

Pascal Leclerc's Oric site: http://pleclerc.free.fr/Oric/OricPage.html

Best regards.

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Post by tingo » Sat Dec 26, 2009 4:22 pm

Interesting. it seems like the DS1230 from Maxim is pin compatible with the 28256 devices. The DS1230 is a static ram device, with battery.
Torfinn

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Post by highwayman » Tue Dec 29, 2009 4:02 am

also more expensive than ferro-ram.

if you want to try a 29f256 then look for very old motherboards.
some used the dip version for the bios.

also old modems, but it's hard to check if they have the right part till you buy them.

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by McOric » Tue Mar 29, 2016 10:57 pm

Sorry to resurrect an old thread, but I am trying to find out if this would this be suitable for programming a 1.1 EEPROM for my Oric1?

http://www.ebay.co.uk/itm/High-Speed-TL ... SwMmBVilXu

Should I go with an EPROM or EEPROM? ROM programming is new to me..

Thanks :)

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by Godzil » Wed Mar 30, 2016 9:36 am

McOric wrote:Sorry to resurrect an old thread, but I am trying to find out if this would this be suitable for programming a 1.1 EEPROM for my Oric1?

http://www.ebay.co.uk/itm/High-Speed-TL ... SwMmBVilXu

Should I go with an EPROM or EEPROM? ROM programming is new to me..

Thanks :)
EPROM/EEPROM will not change how it behave in the oric, only how you erase the chip.

The TL866CS is a good ((E)E)PROM programmer you can buy it safely.

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by McOric » Wed Mar 30, 2016 10:53 am

Thanks Godzil - I'll go ahead and buy the TL866CS.

Is it easier to work with EPROMs or EEPROMs, in terms of erasing & programming?

Godzil wrote:
McOric wrote:Sorry to resurrect an old thread, but I am trying to find out if this would this be suitable for programming a 1.1 EEPROM for my Oric1?

http://www.ebay.co.uk/itm/High-Speed-TL ... SwMmBVilXu

Should I go with an EPROM or EEPROM? ROM programming is new to me..

Thanks :)
EPROM/EEPROM will not change how it behave in the oric, only how you erase the chip.

The TL866CS is a good ((E)E)PROM programmer you can buy it safely.

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by Chema » Wed Mar 30, 2016 12:28 pm

If I recall correctly there were some issues when using an EPROM/EEPROM with the disk drive, as the signal used by the controller to disable the original Rom is used here for programming it.

Silicebit had some small circuitry to overcome this, and there were some other solutions buried in the forums and old sites, but all of them required some modifications (soldering, cutting tracks, adding components...).

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by Godzil » Wed Mar 30, 2016 1:56 pm

McOric wrote:Thanks Godzil - I'll go ahead and buy the TL866CS.

Is it easier to work with EPROMs or EEPROMs, in terms of erasing & programming?
EEPROM as EE mean Electrical Erase (or Eraseable Electrically ;))

The EPROM are the one with the UV glass window.

Chema: yes you are right, as the signal used for ROMDIS on the Oric ROM does not exist on (EE)PROM

It's not really complex, but not necessarily simple to modify an Oric to change the /ROMDIS signal to a proper /OE signal.

What can be done is to:

Remove the LK3 jumber
Cut the track that goes to IC11 pin 10
Solder a 74LS00 in IC11
And connect the ROMDIS signal to IC11 pin 10.

You can also cut the trac that goes out of IC11 pin 3, but that's not really important as it's to drive IC10 /CE.

If you don't wan't to cut any track, the way to do is to use a 74LS00 then:
- Solder +5V and GND correctly to the two VCC/GND Pin.

Take one gate (for example the second one) and:
- connect pin 4 and 5 together to /CSROM (the actual IC11 pin 5)
- then take another gate, like the third one and connect ROMDIS to pin 10
- connect pin 6 to pin 9
- and connect pin 8 to IC11 pin 8

In both case LK3 must be removed.

Pin 27 is used a /PGM on 27C128 and equivalement (EE)PROM chip unlike "ROMDIS" on the Oric ROM. There is normally no risk to change the PROM content to drive that pin low, as it need some high voltage on some specific pins, but if you really want to do things correctly, you would have to cut the track to not make the /ROMDIS signal to go to /PGM and tight PGM to VCC with a resistor (anything between 2K and 10K would work there, lower will add to much to consumption, too high, there are risk that the current is not enough to drive the pin high)

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by Silicebit. » Wed Mar 30, 2016 7:57 pm

This was commented here: http://forum.defence-force.org/viewtopic.php?f=8&t=850

You can do it in this way or use a small PCB described here: http://www.retrowiki.es/fororw/viewtopi ... 35&t=31702
Oric user since 1984. YouTube

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by kenneth » Wed Mar 30, 2016 10:10 pm

It could be interesting to use the w27C512 45z, this memory is EEPROM (no uv eraser required) . This one is four time too big but Oric Basic could be stored in the last fourth (pin1 is A15 to VCC ), but the romdis input will not work if a drive is connected.

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by Godzil » Fri Apr 01, 2016 2:12 am

Silicebit. wrote:This was commented here: http://forum.defence-force.org/viewtopic.php?f=8&t=850

You can do it in this way or use a small PCB described here: http://www.retrowiki.es/fororw/viewtopi ... 35&t=31702
It's easier to change /CS instead of /OE as you just have LK3 to remove and no track to cut, and /PGM need to be high for the EEPROM to work correctly, and not floating.

It's not an issue to drive /CS low and /PGM at the same time. A simple deadbug connection using my second example is the easiest way to do as it will need no cut at all.

And using a 27C512, it will fit, but would need more change on the PCB as pin 1 and pin 27 are address bits so you will need to cut the ROMDIS for sure and also make sure that pin 1 is to the correct voltage (depending on the location in the ROM you want to access)

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Re: EEPROM (or flash) replacement for Oric-1 ROM?

Post by iss » Fri Apr 01, 2016 11:45 am

... and here is one more variant. Some years ago I've created this small adapter pcb for my Pravetz'es to replace PROMs with Atmos 1.1. It's designed for 27128 just because I have lot of them and the idea was to not cut tracks.
rom-sch.jpg
rom-pcb.jpg

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