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Merge pull request #17 from Russell-S-Harper/development
Adding DIV instruction.
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Russell-S-Harper
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a23e168194
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@ -299,12 +299,15 @@ _2 INC _PCL ; advance PC
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_3 RTS
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.)
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_RETZD .( ; clears register D, falls through to _TRFDR
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_RETZD .( ; clears register D, clears underflow, falls through to _TRFDR
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LDA #0
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STA _RD
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STA _RD+1
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STA _RD+2
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STA _RD+3
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LDA _F ; clear underflow
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AND #_F_U^$FF
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STA _F
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.)
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_TRFDR .( ; pulls X, transfers RD to X as r register, updates overflow flag
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@ -424,10 +427,10 @@ _1 LDA _R0,Y ; check for zero argument
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BNE _2 ; q is non-zero
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JMP _RETZD ; q is zero, return zero
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_2 LDA _R0+3,X ; save sign of register p
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AND #%11000000
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AND #_MSK_O
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PHA
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EOR _R0+3,Y
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AND #%11000000 ; save sign of product
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AND #_MSK_O ; save sign of product
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PHA
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JSR _TRFQD
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TXA
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@ -511,8 +514,173 @@ _8 PLA ; reset the sign of register p
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_9 JMP _TRFDR ; pull X, transfer RD to r register, let it handle the return
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.)
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_CMPDC .( ; compare D to C, return result in status
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LDA _RD+3
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CMP _RC+3
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BCC _1 ; definitely less
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BNE _1 ; definitely greater
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LDA _RD+2
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CMP _RC+2
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BCC _1 ; definitely less
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BNE _1 ; definitely greater
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LDA _RD+1
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CMP _RC+1
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BCC _1 ; definitely less
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BNE _1 ; definitely greater
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LDA _RD
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CMP _RC
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_1 RTS
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.)
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_DIV .( ; DIV r pq dr pq Rr <- Rp / Rq - division
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RTS
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TXA
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PHA ; save r register for later
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JSR _GETPQ
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LDA _R0,X ; check for zero argument
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ORA _R0+1,X
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ORA _R0+2,X
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ORA _R0+3,X
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BNE _1 ; p is non-zero
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JMP _RETZD ; p is zero, return zero
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_1 LDA _R0,Y ; check for zero argument
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ORA _R0+1,Y
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ORA _R0+2,Y
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ORA _R0+3,Y
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BNE _2 ; q is non-zero
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BRK ; q is zero, abort and call exception handler (TODO)
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_2 LDA _R0,X ; copy p to RD
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STA _RD
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LDA _R0+1,X
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STA _RD+1
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LDA _R0+2,X
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STA _RD+2
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LDA _R0+3,X
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STA _RD+3
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LDA _R0,Y ; copy q to RC
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STA _RC
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LDA _R0+1,Y
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STA _RC+1
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LDA _R0+2,Y
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STA _RC+2
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LDA _R0+3,Y
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STA _RC+3
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LDA #0 ; set RB to 1
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STA _RB
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LDA #_PLS_1
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STA _RB+1
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LDA #0
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STA _RB+2
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STA _RB+3
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PLA ; restore r register
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TAX
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LDA #0 ; set r to 0
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STA _R0,X
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STA _R0+1,X
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STA _R0+2,X
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STA _R0+3,X
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LDA _RD+3 ; save sign of quotient
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EOR _RC+3
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AND #_MSK_O
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PHA
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LDY #_RD-_R0 ; absolute value of register p saved in D
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JSR _ABSRY
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LDY #_RC-_R0 ; absolute value of register q saved in C
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JSR _ABSRY
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_3 JSR _CMPDC ; is D < C?
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BCC _4 ; yes, continue
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BEQ _5 ; D = C
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ASL _RC ; RC *= 2
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ROL _RC+1
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ROL _RC+2
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ROL _RC+3
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ASL _RB ; RB *= 2
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ROL _RB+1
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ROL _RB+2
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ROL _RB+3
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BCC _3
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; carry is set, means a real overflow condition
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LDA _R0+3,X
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ORA #_F_O
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STA _R0+3,X
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BEQ _4
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JMP _9
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_4 LDA _RB ; is RB > 0?
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ORA _RB+1
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ORA _RB+2
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ORA _RB+3
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BEQ _7 ; no, done
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JSR _CMPDC ; is D >= C?
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BCC _6 ; no, skip subtraction
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_5 SEC ; RD -= RC
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LDA _RD
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SBC _RC
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STA _RD
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LDA _RD+1
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SBC _RC+1
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STA _RD+1
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LDA _RD+2
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SBC _RC+2
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STA _RD+2
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LDA _RD+3
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SBC _RC+3
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STA _RD+3
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CLC ; RX += RB
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LDA _R0,X
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ADC _RB
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STA _R0,X
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LDA _R0+1,X
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ADC _RB+1
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STA _R0+1,X
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LDA _R0+2,X
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ADC _RB+2
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STA _R0+2,X
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LDA _R0+3,X
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ADC _RB+3
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STA _R0+3,X
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LDA _RD ; is RD > 0?
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ORA _RD+1
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ORA _RD+2
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ORA _RD+3
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BEQ _7 ; no, done
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_6 CLC ; RC /= 2
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ROR _RC+3
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ROR _RC+2
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ROR _RC+1
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ROR _RC
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CLC ; RB /= 2
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ROR _RB+3
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ROR _RB+2
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ROR _RB+1
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ROR _RB
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JMP _4
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_7 LDA _R0,X ; check for underflow
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ORA _R0+1,X
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ORA _R0+2,X
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ORA _R0+3,X
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BNE _8 ; non-zero result means no underflow
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LDA _F ; we checked earlier for zero operands, so a zero result means underflow, set underflow
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ORA #_F_U
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STA _F
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BNE _A
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_8 LDA _F ; clear underflow
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AND #_F_U^$FF
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STA _F
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_9 LDA _R0+3,X ; check for overflow
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AND #_MSK_O
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BEQ _A ; all zero, no overflow
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LDA _F ; set overflow
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ORA #_F_O
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STA _F
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BNE _B
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_A LDA _F ; clear overflow
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AND #_F_O^$FF
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STA _F
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_B PLA ; set the sign of quotient
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BEQ _C
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TXA
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TAY
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JSR _NEGRY
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_C RTS
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.)
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_MOD .( ; MOD r pq er pq Rr <- Rp % Rq - modulus
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@ -6,9 +6,9 @@
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; to be able to recognize an overflow/underflow situation, rescale the arguments, and repeat the
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; calculation.
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; Largest value: $3fffffff or 1048575.999(5)
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; Largest value: $3fffffff or +1048575.999(5)
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; Smallest value: $c0000000 or -1048576.000(0)
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; Largest value for DEC/HEX: $3d08ffff or 999999.999
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; Largest value for DEC/HEX: $3d08ffff or +999999.999
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; Smallest value for DEC/HEX: $c2f70001 or -999999.999
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; Instructions
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@ -5,9 +5,10 @@
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HDR(DEMO)
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CMN
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SET(R0, -1023.9995)
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SET(R1, -1023.9995)
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MUL(R2, R0, R1)
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SET(R0, 1023.9995)
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SET(R1, %0.0000000001)
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DIV(R2, R0, R1)
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MUL(R3, R1, R2)
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ESC
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BRK
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