RT-11 idle light pattern

It's been a standard feature of RT-11 FB since it first came out (in V2). You need to set the select switch to display the "Display" register (unlike most other OS idle patterns which rely on the data path display showing R0 when at a WAIT instruction. Here's what it looked like in V2.0 rmonfb.mac: ; "A SOURCE OF INNOCENT MERRIMENT!" ; - W.S. GILBERT, "MIKADO" ; "DID NOTHING IN PARTICULAR, AND DID IT VERY WELL" ; - W.S. GILBERT, "IOLANTHE" ; "TO BE IDLE IS THE ULTIMATE PURPOSE OF THE BUSY" ; - SAMUEL JOHNSON, "THE IDLER" 10$: DEC (PC)+ ;THE RT-11 LIGHTS ROUTINE! 20$: 1 BNE 14$ ;NOT TOO OFTEN ADD #512.,20$ ;RESET COUNT, CLEAR CARRY 16$: ROL 13$ ;JUGGLE THE LIGHTS BNE 11$ ;NOT CLEAR YET COM 13$ ;TURN ON LIGHTS, SET CARRY 11$: BCC 12$ ;NOTHING FELL OFF, KEEP MOVING ADD #100,16$ ;REVERSE DIRECTION BIC #200,16$ ;ROL/ROR FLIP 12$: MOV (PC)+,@(PC)+ ;PUT IN LIGHTS 13$: .WORD 0,SR 14$: MOVB #MXJNUM/2+200,INTACT ;DO A COMPLETE SCAN EXUSLK: BR EXUSER ;BACK INTO LOOKFOR LOOP paul