[Simh] DC11

[Tim Newsham]

> I've got the DC11 ready for testing, but I have a question for the Unix
> V1 team: does the device need to create "correct" parity for input
> characters? That is, does Unix check for odd or even parity, or does it
> just mask input to 7b and proceed?

It checks for parity.  from u9.s:

         mov     rcsr(r0),r2
         mov     rcbr(r0),r1
         tst     r2
         blt     1f / error
         tst     tty+6(r0)
         beq     1f
         bit     $40,r2 / parity
         bne     3f / branch if set
         tstb    tty+4(r0)
         blt     4f / 37 parity not allowed
         br      2f
3:
         bitb    $100,tty+4(r0)
         beq     2f / non-37 parity not allowed
4:

(tty+6 is the stty mode, rcsr is the dc11 read status register, 2f is
the error branch, 4f is success).

> /Bob Supnik

Tim Newsham
http://www.thenewsh.com/~newsham/