27C400/27C800 EPROM emulator

[BlankVector]

I was looking for a solution to update my Amiga ROM (to EmuTOS, of course) and I stumbled on this topic. Very nice device!

[terriblefire]

Can these guys be used in a CDTV?

[valfac]

Hi,

Ist posible to buy one?

Greetings,

[cmorley]

Ist posible to buy one?

Yes details here. I have some left for exxos forum users' projects, PM me.

Can these guys be used in a CDTV?

I don't know much about the CDTV so I just looked at a schematic I downloaded and the kickstart pinout seems to be the same as an Amiga 500. So if it physically fits (I don't know if there is something above the ROM in the CDTV) it should work. The main question I think would be can you hold a CDTV in reset to allow ROM switching - if there is just a monostable that fires on reset then you'll need something else (a switch or something)... if you can hold it in reset like an A500 with ctrl-A-A or on a physical reset button then it should just work (it shouldn't need the reset wire soldering).

As you can tell I really don't know a lot about the CDTV other than what one looks like!

edit: google found some stuff about a single ROM hack with a 27C800 for KS & extended ROM. You would be able to do that too with the eprom emu.

[terriblefire]

Perfect.. that should do the trick.

[gtfan]

Will it work as a replacement for 27C1024 PLCC44 (with proper adapter of course)? It would massively reduce time of tuning car ECU.

[cmorley]

Given the correct adapter electrically it should work. You'd need to tie the unused address lines to ground because 27C1024 is 64Kx16 and 27C200 (smallest EPROM my thing supports) is 128Kx16.

Adapting a DIP to a PLCC socket is a pain though - the other way round is a lot easier.

None of the parts on it are automotive grade for temperature or vibration. (e.g. no flexible MLCC caps) You could maybe use it for dyno work but not in a car on the public road.

[terriblefire]

Hoping someone can tell me what i'm doing wrong here...

Code: Select all

 
****************************************************************
BooBip 27C200/400/800/160 EPROM emulator & ROM switcher
www.BooBip.com

Device          18.011 issue C/D
STM32 firmware  0.8 (C)2020 Chris Morley
CPLD firmware   0.10 (C)2020 Chris Morley
Firmware CRC    70ca0389
STM32 id        dev=0x445, rev=0x1000
STM32 uid       00050011 42504312 20323733
CPLD id         mfg=0x06e, dev=0x20a5, rev=0
FLASH id        mfg=1, dev=0xc4
EPROM type      27C800 (1024KB)
ROM selected    0

and

Code: Select all

                    A17 A18 A19
pull-up              n   n   n
enable               y   y   n
ROM size            27C800 1024KB
intial ROM          0
autosave initial    n
ROM switch pullup   y
wireless ROM switch y
enable LED          y

I have this in an 27C400 socket with the attached binary flashed. A18 from the EPROM is hard wired via dupont cable to VCC or GND.

If i flash the upper and lower halves of the 27C800 space with the same data everything works. Otherwise it never works. In this configuration

Lower 512K | Upper 512K | Wire | Result
DIAGROM | BLANK | GND | WORKS
BLANK | DIAGROM | VCC | FAILS
DIAGROM | DIAGROM | X | WORKS

Can anyone help me here its driving me crazy? I also noted that byteswap is very unreliable.

[cmorley]

You have nothing driving A19 and the pull ups enabled on A17 & A18. A19 is floating.

Code: Select all

                    A17 A18 A19
pull-up              n   n   y
enable               n   n   y
ROM size            27C800 1024KB
intial ROM          0
autosave initial    n
ROM switch pullup   n
wireless ROM switch y
enable LED          y

Use the wizard in the options menu (p - choose preset) to set it for you.

P.S. don't set pull ups on address lines driven externally... ST say this is bad in the STM32 datasheet

edit: the "wireless ROM switch" works by detecting activity on A0 (at the EPROM emu). Do you disable the external address bus when executing "private" cycles? >1.5s of inactivity and it will ROM switch for you. Also powering down/up the Amiga with the USB power attached, the module can't distinguish that from a RESET so watch out for it ROM switching if you're power cycling during dev. Set "wireless ROM switch=n" and set "ROM switch pullup=y" to disable ROM switching with nothing connected to the R pin.

[terriblefire]

OK thanks.. thats helped.

What does Enable A19 do then? it seems redundant?