From 5f29c7c3ebf050004d52f5078013f6f254bb7c15 Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Wed, 23 Aug 2023 15:30:06 +0100
Subject: [PATCH] cpu - Change flags from NZOC to ONZC

---
 cpu.js                   | 24 ++++++++++++------------
 readme.md                | 26 +++++++++++++-------------
 test-programs/keypad.asm |  2 +-
 3 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/cpu.js b/cpu.js
index 91a9d60..d79f5f8 100644
--- a/cpu.js
+++ b/cpu.js
@@ -19,7 +19,7 @@ const CPU = {
   // Core state
   running: false,
   IP: INITIAL_IP_ADDRESS,
-  FLAGS: 0, // A bit field! 0000 = NZOC
+  FLAGS: 0, // A bit field! 0000 = ONZC
   Acc: 0,
   memory: null,
 
@@ -29,13 +29,13 @@ const CPU = {
     CPU.memory = new Uint8Array(256);
     CPU.memory.set(data, 0);
   },
-  setFlagNegative: () => { CPU.FLAGS |= 8 },
-  setFlagZero:     () => { CPU.FLAGS |= 4 },
-  setFlagOverflow: () => { CPU.FLAGS |= 2 },
+  setFlagOverflow: () => { CPU.FLAGS |= 4 },
+  setFlagNegative: () => { CPU.FLAGS |= 4 },
+  setFlagZero:     () => { CPU.FLAGS |= 2 },
   setFlagCarry:    () => { CPU.FLAGS |= 1 },
-  unsetFlagNegative: () => { CPU.FLAGS &= ~8 },
-  unsetFlagZero:     () => { CPU.FLAGS &= ~4 },
-  unsetFlagOverflow: () => { CPU.FLAGS &= ~2 },
+  unsetFlagOverflow: () => { CPU.FLAGS &= ~8 },
+  unsetFlagNegative: () => { CPU.FLAGS &= ~4 },
+  unsetFlagZero:     () => { CPU.FLAGS &= ~2 },
   unsetFlagCarry:    () => { CPU.FLAGS &= ~1 },
   updateFlagZero: () => {
     if (CPU.Acc === 0) {
@@ -107,7 +107,7 @@ const Instructions = {
     // Calculate overflow flag status
     let bitSixCarry = 0;
     if ((CPU.Acc & 64) && (lit & 64)) { bitSixCarry = 1; }
-    let overflow = bitSixCarry ^ (CPU.FLAGS & 1)
+    let overflow = bitSixCarry ^ (CPU.FLAGS & 8);
     if (overflow) {
       CPU.setFlagOverflow();
     } else {
@@ -132,7 +132,7 @@ const Instructions = {
     // Calculate overflow flag status
     let bitSixCarry = 0;
     if ((CPU.Acc & 64) && (addr & 64)) { bitSixCarry = 1; }
-    let overflow = bitSixCarry ^ (CPU.FLAGS & 1)
+    let overflow = bitSixCarry ^ (CPU.FLAGS & 8);
     if (overflow) {
       CPU.setFlagOverflow();
     } else {
@@ -157,7 +157,7 @@ const Instructions = {
     // Calculate overflow flag status
     let bitSixCarry = 0;
     if ((CPU.Acc & 64) && (lit & 64)) { bitSixCarry = 1; }
-    let overflow = bitSixCarry ^ (CPU.FLAGS & 1)
+    let overflow = bitSixCarry ^ (CPU.FLAGS & 8);
     if (overflow) {
       CPU.setFlagOverflow();
     } else {
@@ -182,7 +182,7 @@ const Instructions = {
     // Calculate overflow flag status
     let bitSixCarry = 0;
     if ((CPU.Acc & 64) && (addr & 64)) { bitSixCarry = 1; }
-    let overflow = bitSixCarry ^ (CPU.FLAGS & 1)
+    let overflow = bitSixCarry ^ (CPU.FLAGS & 8);
     if (overflow) {
       CPU.setFlagOverflow();
     } else {
@@ -384,7 +384,7 @@ function logCPUState(debug = false) {
     console.log('Mnemonic:', CPU.currentInstruction.mnemonic);
     console.log(`Machine:  $${num2hex(CPU.currentInstruction.opcode)} $${num2hex(CPU.currentInstruction.operand)}`);
     console.log();
-    console.log(`IP: $${num2hex(CPU.IP)}  Acc: $${num2hex(CPU.Acc)}  NZOC: ${num2bin_4bit(CPU.FLAGS)}`);
+    console.log(`IP: $${num2hex(CPU.IP)}  Acc: $${num2hex(CPU.Acc)}  ONZC: ${num2bin_4bit(CPU.FLAGS)}`);
     console.log(`KEY: $${num2hex(CPU.memory[KEYPAD_ADDR])}  ${CPU.running ? "running" : "halted" }`);
     console.log();
   console.groupEnd();
diff --git a/readme.md b/readme.md
index ab1a725..a41b7c3 100644
--- a/readme.md
+++ b/readme.md
@@ -37,13 +37,13 @@ With single stepping + verbose debugging output:
 
 - `A` - accumulator
 - `IP` - instruction pointer (aka program counter)
-- `FLAGS` - flags: **N**egative, **Z**ero, **O**verflow, **C**arry
+- `FLAGS` - flags: **O**verflow, **N**egative, **Z**ero, **C**arry
     - in machine language, each flag is given a number:
-        - N = 3  
-          Z = 2  
-          O = 1  
+        - O = 3  
+          N = 2  
+          Z = 1  
           C = 0
-    - (bitwise, `0000 = NZOC`)
+    - (bitwise, `0000 = ONZC`)
 
 
 ## Instruction set
@@ -85,21 +85,21 @@ NOP              +2
 
 STO  w           +2
 LDA  r    NZ     +2
-ADD       NZOC   +2
-SUB       NZOC   +2
+ADD       ONZC   +2
+SUB       ONZC   +2
 HOP              +2/+4
 JMP              arg
-FTG       NZOC   +2
-FHP       NZOC   +2/+4
+FTG       ONZC   +2
+FHP       ONZC   +2/+4
 
 STO  r,w         +2
 LDA  r,r  NZ     +2
-ADD  r    NZOC   +2
-SUB  r    NZOC   +2
+ADD  r    ONZC   +2
+SUB  r    ONZC   +2
 HOP  r           +2/+4
 JMP  r           arg
-FTG  r    NZOC   +2
-FHP  r    NZOC   +2/+4
+FTG  r    ONZC   +2
+FHP  r    ONZC   +2/+4
 ```
 
 
diff --git a/test-programs/keypad.asm b/test-programs/keypad.asm
index 79b9cbe..91e7350 100644
--- a/test-programs/keypad.asm
+++ b/test-programs/keypad.asm
@@ -7,7 +7,7 @@
 
 #LOOPCOUNT $80
 
-#Z 2          ; the zero flag is #2
+#Z 1          ; the zero flag is #1
 #keypad   $20 ; magic memory location containing latest key pressed
 #loopIter $FF ; address of loop iterator
 #iterPx   $03 ; where to display iterator