Add inv_FAC1_mantissa

STATUS.md

@@ -211,7 +211,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$B867`   | `add_MEM_FAC1`         | DONE     |                                                    |
 | `$B86A`   | `add_FAC2_FAC1`        | DONE     |                                                    |
 | `$B8FE`   | `normal_FAC1`          | DONE     |                                                    |
-| `$B947`   | `inv_FAC1_mantissa`    | NOT DONE |                                                    |
+| `$B947`   | `inv_FAC1_mantissa`    | DONE     |                                                    |
 | `$B9EA`   | `log_FAC1`             | NOT DONE |                                                    |
 | `$BA28`   | `mul_MEM_FAC1`         | DONE     |                                                    |
 | `$BA2B`   | `mul_FAC2_FAC1`        | DONE     |                                                    |

src/,,config_custom.s

@@ -108,7 +108,7 @@
 ; --- Software features
 
 ;; #CONFIG# PANIC_SCREEN               YES
-;; #CONFIG# DOS_WEDGE                  YES
+;; #CONFIG# DOS_WEDGE                  NO
 ;; #CONFIG# TAPE_WEDGE                 YES
 ;; #CONFIG# TAPE_HEAD_ALIGN            NO
 ;; #CONFIG# BCD_SAFE_INTERRUPTS        YES

src/,,config_testing_60K.s

@@ -97,7 +97,7 @@
 ; --- Software features
 
 ;; #CONFIG# PANIC_SCREEN               YES
-;; #CONFIG# DOS_WEDGE                  YES
+;; #CONFIG# DOS_WEDGE                  NO
 ;; #CONFIG# TAPE_WEDGE                 YES
 ;; #CONFIG# TAPE_HEAD_ALIGN            NO
 ;; #CONFIG# BCD_SAFE_INTERRUPTS        YES

src/basic/math/b947.inv_FAC1_mantissa.s

@@ -12,9 +12,25 @@
 ; - https://sta.c64.org/cbm64basconv.html
 ;
 
-; XXX implement, test
+; 2-complement the FAC1 mantissa
+; The 4 byte mantissa is treated as an integer in big endian form
 
 
 inv_FAC1_mantissa:
 
-	+STUB_IMPLEMENTATION
+    ldx #3
+@1: lda FAC1_mantissa,X
+    eor #$FF
+    sta FAC1_mantissa,X
+    dex
+    bpl @1
+
+    inc FAC1_mantissa+3
+    bne @2
+    inc FAC1_mantissa+2
+    bne @2
+    inc FAC1_mantissa+1
+    bne @2
+    inc FAC1_mantissa
+    
+@2: rts

strings/65D00AE664D006E663D002E66260

@@ -0,0 +1,3 @@
+$65 + BNE $0A + INC $64 + BNE $06 + INC $63 + BNE $02 + INC $62 + RTS
+
+Incrementing a 32-bit integer at the well known position of the FAC1 mantissa in the zero page.

strings/BBA90085

@@ -0,0 +1,3 @@
+fragment + LDA #$00 + STA fragment
+
+Fragments of clearing byte in zero page.

strings/D0034C09

@@ -0,0 +1,3 @@
+BNE $03 + JMP fragment
+
+If zero do jump else not. Common long conditional branch idiom.

testsuite/unit/math.vs

@@ -314,6 +314,41 @@ print "COMPARE"
 compare $61 $66 $1001
 print "END"
 
+print "TEST: inv_FAC1_mantissa 0"
+fill $62 $65 00 00 00 00
+r PC=$B947
+ret
+fill $1001 $1004 00 00 00 00
+print "COMPARE"
+compare $62 $65 $1001
+print "END"
+
+print "TEST: inv_FAC1_mantissa 1"
+fill $62 $65 00 00 00 01
+r PC=$B947
+ret
+fill $1001 $1004 FF FF FF FF
+print "COMPARE"
+compare $62 $65 $1001
+print "END"
+
+print "TEST: inv_FAC1_mantissa 2130706432"
+fill $62 $65 7F 00 00 00
+r PC=$B947
+ret
+fill $1001 $1004 81 00 00 00
+print "COMPARE"
+compare $62 $65 $1001
+print "END"
+
+print "TEST: inv_FAC1_mantissa -100"
+fill $62 $65 FF FF FF 9C
+r PC=$B947
+ret
+fill $1001 $1004 00 00 00 64
+print "COMPARE"
+compare $62 $65 $1001
+print "END"
 
 
 q