> On Dec 25, 2015, at 2:21 AM, Bob Supnik <[email protected]> wrote:
>
> It's worse than that. The detailed logic is shown on 227-5631-0 pp 188ff. The
> decode chart for each decode switch (DSW) is:
>
> DSW 0 0000
> DSW 1 0001
> DSW 2 0010
> DSW 3 X011
> DSW 4 X100
> DSW 5 X101
> DSW 6 X110
> DSW 7 X111
> DSW 8 1XX0
> DSW 9 1XX1
>
> It's quite bizarre, actually. The decode switches are 4-input AND gates (sort
> of), so every decode could have been complete. Instead, the X inputs are not
> wired to anything.
>
> The result is that for invalid digits:
>
> 1010 nothing active, because DSW2 decode is complete
You're right that I didn't look closely enough. As Michael Short points out,
1010 would decode as 8. So for the original question, which is "what happens
with a record mark (1010) in the address" the answer would appear to be that it
is taken as an 8.
And yes, that does assume that some separate logic isn't triggering MAR Error
on that case; I haven't looked.
paul
_______________________________________________
Simh mailing list
[email protected]
http://mailman.trailing-edge.com/mailman/listinfo/simh
