/ entry
1:
       cmp     r2,$bufp / bump all entrys in bufp and put latest assigned
       blos    1f / buffer on the top (this makes if the lowest priority)
       mov     -(r2),2(r2) / job for a particular device
       br      1b
1:
       mov     r5,(r2)
       mov     (sp)+,r2 / restore r2
       rts     r0

tape: / dec tape interrupt
       jsr     r0,setisp / save registers and clockp on stack
       mov     tcstate,r3 / put state of dec tape in r3
       jsr     r0,trapt; tccm; tcap; 4 / busy bit
       mov     r3,pc / device control status register
       / if no errors, go to device state (an address)

taper: / dec tape error
       dec     tcerrc / decrement the number of errors
       bne     1f / if more than 1 branch
       movb    1(r2),r3 / r2+1 points to command register upper byte
       bic     $!7,r3 / clear all but bits 8-10 (Unit Selection)
       incb    deverr+2(r3) / set error bit for this tape unit
       br      tape3
1: / more than 1 error
       bit     $4000,(r2) / direction of tape
       beq     1f / if forward go to 1f
       bic     $4000,(r2) / reverse, set to forward
       mov     $tape1,tcstate / put tape 1 in the state
       br      0f
1: / put tape in reverse
       bis     $4000,(r2) / set tape to reverse direction
       mov     $tape2,tcstate / put tape 2 as the state
0:
       bis     $4,active / check active bit of tape
       movb    $103,(r2) / set read function and interrupt enable
       br      4f / go to retisp
tape1: / read bn forward
       mov     $tcdt,r0 / move address of data register to r0
       cmp     (r0),2(r1) / compare block addresses
       blt     0b / if lt, keep moving
       bgt     taper / if gt, reverse
       mov     6(r1),-(r0) / put bus address in tcba
       mov     4(r1),-(r0) / put word count in tcwc
       mov     $115,-(sp) / put end interrupt enable
       bit     $20000,(r1) / is "waiting to read bit" of I/O queue set?
       beq     1f / no,  1f
       mov     $105,(sp) / yes, put and interrupt enable
1:
       movb    (sp)+,(r2) / move function into command register (tccm)
       bis     $4,active / set active bit
       mov     $tape3,tcstate / get ready for I/O transfer
       br      4f / go to retisp (rti)

tape2: / read bn bakasswards