Mercurial > hg > Members > kono > nitros9-code
view lib/alib/div16x16.a @ 2736:31cd1f1b4fb0 lwtools-port
Added ClrScrn and CapsLock functionality for Atari VTIO
author | Boisy Pitre <boisy.pitre@nuance.com> |
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date | Mon, 10 Dec 2012 16:27:38 -0600 (2012-12-10) |
parents | 7d70b7e1cb21 |
children | aaba193af04f |
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********************************************* * 16 x 16 bit integer divide * OTHER MODULES NEEDED: none * ENTRY: D = divisor * X = dividend * EXIT: X = quotient * D = remainder nam 16x16 bit Divide ttl Assembler Library Module psect DIV16,0,0,0,0,0 vsect negcount rmb 1 endsect * Signed Divide SDIV16: clr negcount,u PSHS D,X tst ,s bpl testquo ldd ,s comb coma addd #$0001 std ,s inc negcount,u testquo tst 2,s bpl ok ldd 2,s comb coma addd #$0001 std 2,s inc negcount,u ok puls d,x bsr DIV16 dec negcount,u bne goforit pshs d,x ldd ,s coma comb addd #$0001 std ,s ldd 2,s coma comb addd #$0001 std 2,s puls d,x goforit rts * Unsigned Divide DIV16: PSHS D,X save divisor & dividend LDA #16 bit counter PSHS A CLRA initialize remainder CLRB div1 ASL 4,S shift dividend & quotient ROL 3,S ROLB shift dividend into B ROLA CMPD 1,S trial subtraction reqd? BLO div2 SUBD 1,S yes, do subtraction INC 4,S increment quotient div2 DEC ,S count down another bit BNE div1 LDX 3,S get quotient LEAS 5,S clean stack RTS endsect