Mercurial > hg > Members > kono > nitros9-code
view lib/alib/mult16x16.as @ 3140:03b580a02945
Allow CoCo3FPGA-specific build of superdesc.asm
Added new conditional CC3FPGA and code to "level1/modules/superdesc.asm"
to reflect changes needed to build the new SD card descriptors for the
Coco3FPGA.
| author | Bill Pierce <merlinious999@gmail.com> |
|---|---|
| date | Sat, 04 Feb 2017 11:06:26 +0100 |
| parents | 03f26e88b809 |
| children |
line wrap: on
line source
************************************ * 16 x 16 Multiply * ENTRY: D = multiplier * X = multiplicand * EXIT: Y = product 2 msbs * U = " 2 lsbs * D & X preserved nam 16x16 bit Multiply ttl Assembler Library Module section .text MULT16: PSHS D,X,Y,U save #s and make stack room CLR 4,S reset overflow flag LDA 3,S get byte MUL STD 6,S save B x Xl LDD 1,S MUL B x Xh ADDB 6,S ADCA #0 STD 5,S add 1st 2 mult. LDB 0,S LDA 3,S MUL A x Xl ADDD 5,S STD 5,S add result to previous BCC no.ov branch if no overflow INC 4,S set overflow flag no.ov LDA 0,S LDB 2,S MUL A x Xh ADDD 4,S STD 4,S PULS D,X,Y,U,PC return endsect