[sdiy] pd650 - do all the Roland applicaitons use an identical chip?

[Rainer Buchty]

>Seems like Roland would be cautious about having their code copied.

Why?

First, that family of controllers seems to be ROM-only. IP law aside, 
the average Joe couldn't just copy the code and build a clone. And even 
if he could, they would play the same game on him and just read the 
thingy out, make a code comparison, and unleash the lawyers afterwards.

I bet, all they cared about was price (and maybe Japanese source).

To make reading out harder, it might be that all the uPD650 offers is a 
verify mode: you bring up that thing in diagnostic mode, apply a data 
word at those 8 data pins, clock it -- and a (mis)match will be 
signalled by one of the output pins. Maybe a mismatch will also lock the 
unit, i.e. you would have to reset it again to re-start reading out.

That way, it would take 256 clock cycles per byte (plus eventual reset) 
to find the proper content, but since we're just dealing with 2k, time 
should not be an issue.

Given the age and the overall "complexity" of this architecture, I 
somehow doubt they dedicated a significant amount of chip space to 
security. 

Now if someone has a clue about how to rip code off a 6500/11... (My 
guess is that test mode signalling is done on PA, possibly PA0. It 
magically appears as "input data strobe" on one illustration, but isn't 
specifically shown in the block view, which in term shows an edge 
detector sitting next to PA.)

Rainer