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

[Colin f]

> Some of the problems the Roland mask ROM's (HD61256P) present;
> 
> -Address-lines are mixed up from jadec standard. My present 
> meathod or 
> re-ordering the address-pins so my eprom programmer can read 
> them is by 
> breadboarding the Roland ROM and running wires to the correct 
> locations on 
> my programmer (messy & 28 of 'em, but solves the problem).

I wrote a Windows utility to do this.
It takes a map file for the address and data lines, then re-writes a .bin
file as required.
The program is somewhat rough and ready, but does the job.
I'll try to get it uploaded to my website when I have some spare time.
 
> -Roland's CS (chip select) is pin 26 while pin 20 is an 
> address pin. These 
> need to be swapped to match 27c256 standard pinout. (Fix as above)

And on the 909, some ROMs have active high chip select, while others are
active low.
But you can fix that with a simple jumper wire to an inverted output on the
IC that drives the line.
 
> -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.

I don't remember that being the case - if it is on the mask ROMs, it won't
be on an EPROM.

Cheers,
Colin f