8085 vs 8085A

[Chuck Guzis]

On 6 Aug 2007 at 15:30, Allison wrote:

> 8085 was 1977 and the 8085A from what I have was soon before!  Date 
> codes suggest late  1977 (week 52 1977) for one 8085A.   I suspect
> the differnces are processing only and they are interchangeable.

As part of a group that was developing systems using the 8085 
starting in late 1976 using pre-production steppings, I believe that 
I can state with fair certainty that there were differences.  The 
timing of the select outputs is sligtly different and there is a race 
condition (IIRC) between the TRAP and x.5 interrupts.  The 8085A took 
care of these--and we dropped the additional "glue" to fix the 
problems when we went to the second revision of the CPU board and the 
AH HCMOS parts.

While it's true that you can always use an 8085A in a board designed 
for an 8085 part, the converse is not true.

Cheers,
Chuck