All I can think off is that old school rule devision is multiplying with the inverse... For a 16 bit value this would imply a 64kb 
table to quickly convert a number X to 1/X and subsequently use the the above singed multiplication routine. Possibly only for use on r800.
I did use muluw for some fixed devision (unsigned) some time ago... let me look it up...
found it!
;--------------------------------------------------- ; 16 bit - div 12 ;mod 12 ; ; valid value range 0 - 12288 ; ; in: hl uit: hl = div 12 , e = mod 12 ; ; verandert: a,bc,de,hl divmod12 ld bc,5461 ; 65536 / 12 muluw hl,bc push de ; >>> bewaar div 12 /* ld a,21 ; afronding fout correctie grote getallen add a,h ld h,a */ ld bc,12 ; rest x 12 = mod muluw hl,bc pop hl ; <<< ret
Does also calculate the reminder. Does not help you though. 
Untested, but basically it is GosthwriterP's code on 8 bits
; fastdiv ; input: E=dividend, C=divisor ; output: E=quotient, H=rest/divisor*256 fastdiv: xor a ld d,a ld b,a ld hl,HelpTable-1 add hl,bc ld c,(hl) inc hl ld b,(hl) ex de,hl muluw hl,bc ret HelpTable: ; dw 2^16/i = 1..255 dw 65536 dw 32768 dw 21845 dw 16384 dw 13107 dw 10923 dw 9362 dw 8192 dw 7282 dw 6554 dw 5958 dw 5461 dw 5041 dw 4681 dw 4369 dw 4096 dw 3855 dw 3641 dw 3449 dw 3277 dw 3121 dw 2979 dw 2849 dw 2731 dw 2621 dw 2521 dw 2427 dw 2341 dw 2260 dw 2185 dw 2114 dw 2048 dw 1986 dw 1928 dw 1872 dw 1820 dw 1771 dw 1725 dw 1680 dw 1638 dw 1598 dw 1560 dw 1524 dw 1489 dw 1456 dw 1425 dw 1394 dw 1365 dw 1337 dw 1311 dw 1285 dw 1260 dw 1237 dw 1214 dw 1192 dw 1170 dw 1150 dw 1130 dw 1111 dw 1092 dw 1074 dw 1057 dw 1040 dw 1024 dw 1008 dw 993 dw 978 dw 964 dw 950 dw 936 dw 923 dw 910 dw 898 dw 886 dw 874 dw 862 dw 851 dw 840 dw 830 dw 819 dw 809 dw 799 dw 790 dw 780 dw 771 dw 762 dw 753 dw 745 dw 736 dw 728 dw 720 dw 712 dw 705 dw 697 dw 690 dw 683 dw 676 dw 669 dw 662 dw 655 dw 649 dw 643 dw 636 dw 630 dw 624 dw 618 dw 612 dw 607 dw 601 dw 596 dw 590 dw 585 dw 580 dw 575 dw 570 dw 565 dw 560 dw 555 dw 551 dw 546 dw 542 dw 537 dw 533 dw 529 dw 524 dw 520 dw 516 dw 512 dw 508 dw 504 dw 500 dw 496 dw 493 dw 489 dw 485 dw 482 dw 478 dw 475 dw 471 dw 468 dw 465 dw 462 dw 458 dw 455 dw 452 dw 449 dw 446 dw 443 dw 440 dw 437 dw 434 dw 431 dw 428 dw 426 dw 423 dw 420 dw 417 dw 415 dw 412 dw 410 dw 407 dw 405 dw 402 dw 400 dw 397 dw 395 dw 392 dw 390 dw 388 dw 386 dw 383 dw 381 dw 379 dw 377 dw 374 dw 372 dw 370 dw 368 dw 366 dw 364 dw 362 dw 360 dw 358 dw 356 dw 354 dw 352 dw 350 dw 349 dw 347 dw 345 dw 343 dw 341 dw 340 dw 338 dw 336 dw 334 dw 333 dw 331 dw 329 dw 328 dw 326 dw 324 dw 323 dw 321 dw 320 dw 318 dw 317 dw 315 dw 314 dw 312 dw 311 dw 309 dw 308 dw 306 dw 305 dw 303 dw 302 dw 301 dw 299 dw 298 dw 297 dw 295 dw 294 dw 293 dw 291 dw 290 dw 289 dw 287 dw 286 dw 285 dw 284 dw 282 dw 281 dw 280 dw 279 dw 278 dw 277 dw 275 dw 274 dw 273 dw 272 dw 271 dw 270 dw 269 dw 267 dw 266 dw 265 dw 264 dw 263 dw 262 dw 261 dw 260 dw 259 dw 258 dw 257
Thinking to the signed version (for z80)
ログイン（登録）してコメントを投稿