UNIX 6th Ed. - /usr/source/mdec/tc.s

   1: tcdt = 177350
   2: tccm = 177342
   3: tread:
   4:         mov     $tcdt,r0
   5:         mov     $tccm,r1
   6: for:
   7:         mov     $3,(r1)                 / rbn for
   8: 1:
   9:         tstb    (r1)
  10:         bge     1b
  11:         tst     (r1)
  12:         blt     rev
  13:         cmp     tapa,(r0)
  14:         beq     rd
  15:         bgt     for
  16: 
  17: rev:
  18:         mov     $4003,(r1)              / rbn bac
  19: 1:
  20:         tstb    (r1)
  21:         bge     1b
  22:         tst     (r1)
  23:         blt     for
  24:         mov     (r0),r2
  25:         add     $5,r2
  26:         cmp     tapa,r2
  27:         blt     rev
  28:         br      for
  29: 
  30: rd:
  31:         mov     ba,-(r0)                        / bus addr
  32:         mov     wc,-(r0)                        / wc
  33:         mov     $5,-(r0)                        / read
  34: 1:
  35:         tstb    (r1)
  36:         bge     1b
  37:         tst     (r1)
  38:         blt     tread
  39:         rts     pc
  40: 
  41: rew:
  42:         mov     $4003,tccm
  43:         rts     pc

Defined functions