[sdiy] Roland Mask ROM's (i.e 707, 909) read/write

[Plutoniq9]

Hi Roy,

I wish it was an easy fix like that, but it seems like Roland purposely made 
in difficult to read their ROM's & to roll-your-own. I'm sure the Oberheim 
prommer was widely available at the time & I know their existed businesses 
which sold replacement sounds for older ROM drum machines.....
I think Roand were thinking "how are we gonna sell the 505 or 626 which have 
"new sounds" when people can upgrade their current machines", that's just a 
theory of course. The other reason is they probably wanted to protect their 
sounds from being ripped off.

The main issue is the blasted clocking of the output-enable pin, normal 
eprom's don't funtion this way so eprom programmers won't probably have that 
ability. I stumbled upon the OE clock requirement when i connected it to A0 
(address-line), which at least outputs a clock on every odd number....before 
that i couldn't even get it to dump any data at all.

I've also verified the strange requirment in the 909 schematics, the OE (pin 
22) of the hihats ROM is connected the the address-counter clock.

Thanks

Ryan


>On Tuesday 04 April 2006 04:08 am, Plutoniq9 wrote:

> > -The final problem, and most frustrating, is that pin 22 (Output-enable 
>or
> > chip-enable) actually needs to be clocked in order for the data pins to
> > output data, you can't just tie it high or low. When the pulse goes high
> > (on every pulse), out comes the data.
> >
> > The last issue is where I'm stuck. In the 909 or certain 707 ROM's, Pin 
>22
> > (OE) is pulsed by the same clock that drives the address counters. 
>However,
> > in a normal eprom programmer, this pin is normally just taken 
>low.....How
> > am i supposed to clock this line and have it in sync with my address
> > counter in the my programmer? I'm stumped, Roland sure made it
> > difficult......
>
>I have NO idea if what I'm going to mention here applies to this specific
>model of equipment or not,  it's just something I bumped into once...
>
>We were a Roland service center.  One time we were doing a "software 
>upgrade"
>on some keyboard,  and the original part pulled was an EPROM,  the new
>replacement was a masked ROM.  And it didn't work.  After putting it in
>there,  the unit was completely dead.  So I called 'em...
>
>(This was one of the real irritations about dealing with Roland,  no 
>toll-free
>tech support,  and it took a while to get a tech on the phone,  and the 
>info
>should've been sent out with the upgrade on a paper anyhow!)
>
>What I was told was that I had to move two "jumpers" which actually 
>consisted
>of two "zero-ohm resistors" that were surface-mount,  which sat right next 
>to
>the part in question.  They were on one set of pads,  and I needed to move
>them to this other set of pads.
>
>Maybe,  if you're lucky,  the board you're messing with has such an
>arrangement?
>
>--
>Member of the toughest, meanest, deadliest, most unrelenting -- and
>ablest -- form of life in this section of space,  a critter that can
>be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
>-
>Information is more dangerous than cannon to a society ruled by lies. 
>--James
>M Dakin
>