From 7ac0d7e04a69b1b4825e6f95238bdd2b804eebb5 Mon Sep 17 00:00:00 2001
From: Russell-S-Harper <russell.s.harper@gmail.com>
Date: Fri, 14 Sep 2018 06:24:35 -0400
Subject: [PATCH] Adding CMR instruction.

---
 common/common.asm | 41 ++++++++++++++++++++++++++++++++---------
 common/common.h   |  1 +
 common/page6.src  |  4 +++-
 3 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/common/common.asm b/common/common.asm
index eb15dd7..6a7bea6 100644
--- a/common/common.asm
+++ b/common/common.asm
@@ -416,12 +416,9 @@ _ADD	.(		; ADD r pq		ar pq		Rr <- Rp + Rq	- addition
 	JMP _RETI0X	; pull X, transfer I0 to r register, let it handle the return
 .)
 
-_SUB	.(		; SUB r pq		br pq		Rr <- Rp - Rq	- subtraction
-	TXA
-	PHA		; save r register for later
-	JSR _GETPQF
-	SEC		; set I0 to Rp - Rq
-	LDA _R0,X
+_SBXYI0	.(		; set I0 to register pointed by X - register pointed by Y
+	LDA _R0,X	; set I0 to Rp - Rq
+	SEC
 	SBC _R0,Y
 	STA _I0
 	LDA _R0+1,X
@@ -433,12 +430,20 @@ _SUB	.(		; SUB r pq		br pq		Rr <- Rp - Rq	- subtraction
 	LDA _R0+3,X
 	SBC _R0+3,Y
 	STA _I0+3
+	RTS
+.)
+
+_SUB	.(		; SUB r pq		br pq		Rr <- Rp - Rq	- subtraction
+	TXA
+	PHA		; save r register for later
+	JSR _GETPQF
+	JSR _SBXYI0
 	JMP _RETI0X	; pull X, transfer I0 to r register, let it handle the return
 .)
 
 _NEGX	.(		; negates register at X
-	SEC
 	LDA #0
+	SEC
 	SBC _R0,X
 	STA _R0,X
 	LDA #0
@@ -704,8 +709,8 @@ _1	RTS
 .)
 
 _UPDDM	.(		; update DIV and MOD
-	SEC		; I0/I1 -= I2/I3
-	LDA _I0
+	LDA _I0		; I0/I1 -= I2/I3
+	SEC
 	SBC _I2
 	STA _I0
 	LDA _I0+1
@@ -987,6 +992,24 @@ _SVI	.(		; SVI pq		0e pq		(Rp:bbcc) <- Rq	- save indirect to memory
 .)
 
 _CMR	.(		; CMR pq		0f pq		F <- Rp <=> Rq	- compare registers
+	JSR _GETPQF
+	JSR _SBXYI0
+	LDA _F
+	AND #_MSK_C	; clear CMR bits
+	STA _F
+	LDA _I0+3	; check highest byte
+	BMI _1		; is less than
+	ORA _I0+2	; could be greater than or equal to, OR with all other bytes
+	ORA _I0+1
+	ORA _I0
+	BNE _2		; is greater than
+	LDA #_F_E	; set equal to flag
+	BNE _3
+_1	LDA #_F_L	; set less than flag
+	BNE _3
+_2	LDA #_F_G	; set greater than flag
+_3	ORA _F
+	STA _F
 	RTS
 .)
 
diff --git a/common/common.h b/common/common.h
index 8e557cf..c3661e0 100644
--- a/common/common.h
+++ b/common/common.h
@@ -138,5 +138,6 @@ _EXT_C	= $f0
 _MSK_O	= %11000000			; mask for overflow
 _MSK_R	= %00111100			; mask for registers
 _MSK_T	= (_F_Z + _F_P + _F_N)^$ff	; mask for TST
+_MSK_C	= (_F_E + _F_G + _F_L)^$ff	; mask for CMP
 
 #endif /* __COMMON_H */
diff --git a/common/page6.src b/common/page6.src
index d046137..f9475a5 100644
--- a/common/page6.src
+++ b/common/page6.src
@@ -6,7 +6,9 @@
 
 HDR(DEMO)
 	CMN
-	BRA(FACTORIAL)
+	SET(R0, 999999.999)
+	SET(R1, -999999.999)
+	CMR(R0, R1)
 	ESC
 	BRK