TRIPOS PDP-11 Assembler version 1.4 ; Constants about machine. 020000 COREND = 8.*1024. ; First unusable word 002000 WIDTH = 1024. ; Height of display 001400 HEIGHT = 768. ; Width of display ; Address of registers. 172000 DPC = 172000 ; VT40 Program counter 172002 DSR = 172002 ; VT40 Status register 172004 XSR = 172004 ; X status register 172006 YSR = 172006 ; Y status register ; Recommended mnemomics 100000 CHAR = 100000 ; Character mode 104000 SHORTV = 104000 ; Short vector mode 110000 LONGV = 110000 ; Long vector mode 114000 POINT = 114000 ; Point mode 120000 GRAPHX = 120000 ; Graphplot X mode 124000 GRAPHY = 124000 ; Graphplot Y mode 130000 RELATV = 130000 ; Relative point mode 002000 INT0 = 2000 ; Intensity modes 002200 INT1 = 2200 002400 INT2 = 2400 002600 INT3 = 2600 003000 INT4 = 3000 003200 INT5 = 3200 003400 INT6 = 3400 003600 INT7 = 3600 000100 LPOFF = 100 ; Light pen off 000140 LPON = 140 ; and on 000020 BLKOFF = 20 ; Blink off 000030 BLKON = 30 ; and on 000004 LINE0 = 4 ; Solid line 000005 LINE1 = 5 ; Long dash 000006 LINE2 = 6 ; Short dash 000007 LINE3 = 7 ; Dot dash 160000 DJMP = 160000 ; Display jump 164000 DNOP = 164000 ; Display NOP 170000 STATSA = 170000 ; Load status A 173400 DSTOP = 173400 ; Display stop and interrupt 001400 SINON = 1400 ; Stop interrupt on 001000 SINOFF = 1000 ; Stop interrupt off 000200 LPLITE = 200 ; Light pen hit on 000300 LPDARK = 300 ; and off 000040 ITAL0 = 40 ; Italics off 000060 ITAL1 = 60 ; and on 000004 SYNC = 4 ; Halt and resume in Sync 174000 STATSB = 174000 ; Load status B 000100 INCR = 100 ; Graphplot increment 040000 INTX = 40000 ; Intensify vector or point 001777 MAXX = 1777 ; Max delta-x 001377 MAXY = 1377 ; Max delta-y 020000 MINUSX = 20000 ; -ve delta-x 020000 MINUSY = 20000 ; -ve delta-y 017600 MAXSX = 17600 ; Max delta-x in short mode 000077 MAXSY = 77 ; Max delta-y 020000 MISVX = 20000 ; -ve delta-x 000100 MISVY = 100 ; -ve delta-y 000000' .PSECT ; Simple PDP-11 program 000000' 012706 017776 MOV #COREND-2,SP ; Set up stack ; R2 - x ; R3 - DPC when writing display file 000004' 012703 000176' MAIN: MOV #END,R3 ; where to start writing point data 000010' 005002 CLR R2 ; start x at 0 000012' LOOP: ; compute next point on graph 000012' 010200 MOV R2,R0 000014' 004767 000052 JSR PC,SQRT ; validate return value 000020' 032701 176000 BIT #176000,R1 ; Y range check - max 10 bits 000024' 001016 BNE BOOB 000026' 010123 MOV R1,(R3)+ 000030' 005202 INC R2 000032' 022702 001777 CMP #WIDTH-1,R2 000036' 100365 BPL LOOP ; loop until x>WIDTH-1 000040' DISPLAY: 000040' 012723 160000 MOV #DJMP,(R3)+ ; fix up end of display program 000044' 012723 000166' MOV #DLOOP,(R3)+ 000050' 012737 000164' 172000 MOV #DPROG,@#DPC ; start displayprocessor runnig 000056' 000001 WAIT ; for ever 000060' 000000 HALT 000062' BOOB: ; Got a duff value from sqrt! 000062' 012737 000001 172002 MOV #1,@#DSR ; Beep! 000070' 000763 BR DISPLAY ; Integer square root, Martin Guy, June 1988. ; Negative arguments are simply negated to make things easy. ; Status: works for arguments -32767 to +32767 ; Argument in R0 -> result in R1, remainder in R0 ; R0 op ; R1 res ; R2 one ; R3 tmp (op-res-one) 000072' SQRT: ; validate argument 000072' 005700 TST R0 000074' 001431 BEQ SQRT1 ; if (op == 0) return(0); 000076' 100001 BPL SQRT2 ; op = abs(op) 000100' 005400 NEG R0 ; preserve temporary registers 000102' 010246 SQRT2: MOV R2,-(SP) ; preserve temporaries 000104' 010346 MOV R3,-(SP) ; initialise: res = 0; op = highest power of 4 <= op 000106' 005001 CLR R1 000110' 012702 040000 MOV #40000,R2 000114' 000402 BR SQRT4 000116' 006202 SQRT3: ASR R2 000120' 006202 ASR R2 000122' 020002 SQRT4: CMP R0,R2 000124' 100774 BMI SQRT3 ; loop until one <= op (R2 <= R0) ; ie until (R0 - R2) is positive or 0 ; main sqrt loop 000126' 010003 SQRT5: MOV R0,R3 ; op2 = op -res - one 000130' 160103 SUB R1,R3 000132' 006201 ASR R1 ; loop reinit moved here from end for speed 000134' 160203 SUB R2,R3 000136' 100402 BMI SQRT6 ; can't do it if it underflowed ; it can happen - do it. 000140' 010300 MOV R3,R0 ; op = op2 000142' 060201 ADD R2,R1 ; res += 2 * one (+=1*one cos R1 already >>) 000144' SQRT6: 000144' 006202 ASR R2 ; one >>= 2 000146' 006202 ASR R2 000150' 001366 BNE SQRT5 ; while (one > 0); ; all done 000152' 012603 MOV (SP)+,R3 000154' 012602 MOV (SP)+,R2 000156' 000207 RTS PC ; Code fragment: 000160' SQRT1: 000160' 005001 CLR R1 000162' 000207 RTS PC ; end of SQRT 000164' DPROG: 000164' 174101 STATSB+INCR+1 000166' 114000 DLOOP: POINT 000170' 000000 0 000172' 000000 0 000174' 124000 GRAPHY 000176' END: .END No errors detected Assembly statistics (words): Absolute Relocatable Code 0 63 Reloc. info 0 3 Space used for symbol table: 1070 words Total workspace used: 1273 words Assembly complete