@@ -31,6 +31,7 @@ cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn

 ### Operator modes

 - `,1234 ,0001 ADD^`, 16-bits operators have the short flag `^`.

+- `,12 ,11 GTH JMP?`, conditional operators have the cond flag `?`.

 ```

 ( hello world )

@@ -41,14 +42,19 @@ cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn

 |0100 @RESET

-"hello

+@word1 "hello_word ( len: 0x0b )

 @loop

-	,dev1w STR

-	,incr JSU ( call incr )

-	,05 NEQ ,loop ROT JSC

+	,dev1w STR ( write to stdout )

+	,incr JSR ( increment itr )

+	,word1 ,strlen JSR ( get strlen )

+	NEQ ,loop ROT JSR? ( loop != strlen )

-BRK ( RESET )

+BRK

+

+@strlen

+	,0001 ADD^ LDR

+	RTS

 @incr

 	,iterator LDR

@@ -56,7 +62,7 @@ BRK ( RESET )

 	,iterator STR 

 	,iterator LDR

 	RTS

-	

+

 |c000 @FRAME BRK 

 |d000 @ERROR BRK 

 |FFFA .RESET .FRAME .ERROR

@@ -66,10 +72,8 @@ BRK ( RESET )

 ### Assembler

-- Create a benchmark file

 - Implement shorthand operators

 - Signed operations

-- zero-page address?

 ### CPU

@@ -77,6 +81,7 @@ BRK ( RESET )

 - Catch overflow/underflow

 - A Three-Way Decision Routine(http://www.6502.org/tutorials/compare_instructions.html)

 - Draw pixel to screen

+- Redo overflow/underflow mappping

 - Detect mouse click

 - SDL Layer Emulator

 - Build PPU

@@ -14,5 +14,5 @@ cc -std=c89 -DDEBUG -Wall -Wno-unknown-pragmas -Wpedantic -Wshadow -Wextra -Werr

 cc -std=c89 -DDEBUG -Wall -Wno-unknown-pragmas -Wpedantic -Wshadow -Wextra -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion -Wvla -g -Og -fsanitize=address -fsanitize=undefined uxn.c -o uxn

 # run

-./uxnasm examples/benchmark.usm boot.rom

+./uxnasm examples/hello.usm boot.rom

 ./uxn boot.rom

@@ -10,22 +10,22 @@

 @loop

 	,dev1w STR ( write to stdout )

-	,incr JSU ( increment itr )

-	,word1 ,strlen JSU ( get strlen )

-	NEQ ,loop ROT JSC ( loop != strlen )

+	,incr JSR ( increment itr )

+	,word1 ,strlen JSR ( get strlen )

+	NEQ ,loop ROT JSR? ( loop != strlen )

 BRK

 @strlen

 	,0001 ADD^ LDR

-	RTU

+	RTS

 @incr

 	,iterator LDR

 	,01 ADD

 	,iterator STR 

 	,iterator LDR

-	RTU

+	RTS

 |c000 @FRAME BRK 

 |d000 @ERROR BRK 

@@ -14,7 +14,7 @@ WITH REGARD TO THIS SOFTWARE.

 #define FLAG_HALT 0x01

 #define FLAG_SHORT 0x02

 #define FLAG_SIGN 0x04

-#define FLAG_TRAPS 0x08

+#define FLAG_COND 0x08

 typedef unsigned char Uint8;

 typedef unsigned short Uint16;

@@ -92,8 +92,6 @@ echom(Memory *m, Uint8 len, char *name)

 /* clang-format off */

 Uint16 bytes2short(Uint8 a, Uint8 b) { return (a << 8) + b; }

-Uint8 rampeek8(Uint16 s) { return cpu.ram.dat[s] & 0xff; }

-Uint8 mempeek8(Uint16 s) { return cpu.ram.dat[s]; }

 Uint16 mempeek16(Uint16 s) { return (cpu.ram.dat[s] << 8) + (cpu.ram.dat[s+1] & 0xff); }

 void wspush8(Uint8 b) { cpu.wst.dat[cpu.wst.ptr++] = b; }

 void wspush16(Uint16 s) { wspush8(s >> 8); wspush8(s & 0xff); }

@@ -107,16 +105,13 @@ void rspush16(Uint16 a) { cpu.rst.dat[cpu.rst.ptr++] = a; }

 /* I/O */

 void op_brk() { setflag(FLAG_HALT, 1); }

 void op_lit() { cpu.literal += cpu.ram.dat[cpu.ram.ptr++]; }

-void op_nop() { }

+void op_nop() { printf("NOP");}

 void op_ldr() { wspush8(cpu.ram.dat[wspop16()]); }

 void op_str() { cpu.ram.dat[wspop16()] = wspop8(); }

 /* Logic */

-void op_jmu() { cpu.ram.ptr = wspop16(); }

-void op_jmc() { Uint8 a = wspop8(); if(a) op_jmu(); }

-void op_jsu() { rspush16(cpu.ram.ptr); cpu.ram.ptr = wspop16(); }

-void op_jsc() { Uint8 a = wspop8(); if(a) op_jsu(); }

-void op_rtu() {	cpu.ram.ptr = rspop16(); }

-void op_rtc() {	/* TODO */ }

+void op_jmp() { cpu.ram.ptr = wspop16(); }

+void op_jsr() { rspush16(cpu.ram.ptr); cpu.ram.ptr = wspop16(); }

+void op_rts() {	cpu.ram.ptr = rspop16(); }

 /* Stack */

 void op_pop() { wspop8(); }

 void op_dup() { wspush8(wspeek8(1)); }

@@ -156,14 +151,14 @@ void op_lth16() { Uint16 a = wspop16(), b = wspop16(); wspush8(b < a); }

 void (*ops[])() = {

 	op_brk, op_lit, op_nop, op_nop, op_nop, op_nop, op_ldr, op_str, 

-	op_jmu, op_jmc, op_jsu, op_jsc, op_rtu, op_rtc, op_nop, op_nop, 

+	op_jmp, op_jsr, op_nop, op_rts, op_nop, op_nop, op_nop, op_nop, 

 	op_pop, op_dup, op_swp, op_ovr, op_rot, op_and, op_ora, op_rol,

 	op_add, op_sub, op_mul, op_div, op_equ, op_neq, op_gth, op_lth,

 	op_pop16, op_dup16, op_swp16, op_ovr16, op_rot16, op_and16, op_ora16, op_rol16,

 	op_add16, op_sub16, op_mul16, op_div16, op_equ16, op_neq16, op_gth16, op_lth16

 };

-Uint8 opr[][2] = { 

+Uint8 opr[][2] = { /* TODO */

 	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0},

 	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0},

 	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0},

@@ -202,8 +197,7 @@ opc(Uint8 src, Uint8 *op)

 int

 eval(void)

 {

-	Uint8 instr = cpu.ram.dat[cpu.ram.ptr++];

-	Uint8 op;

+	Uint8 op, instr = cpu.ram.dat[cpu.ram.ptr++];

 	/* when literal */

 	if(cpu.literal > 0) {

 		wspush8(instr);

@@ -213,19 +207,23 @@ eval(void)

 	/* when opcode */

 	opc(instr, &op);

 	setflag(FLAG_SHORT, (instr >> 5) & 1);

-	setflag(FLAG_SIGN, (instr >> 6) & 1);

-	if((instr >> 7) & 1)

-		printf("Unused flag: %02x\n", instr);

+	setflag(FLAG_SIGN, (instr >> 6) & 1); /* TODO: Implement */

+	setflag(FLAG_COND, (instr >> 7) & 1);

+	/* TODO: overflow */

 	if(cpu.wst.ptr < opr[op][0])

 		return error("Stack underflow", op);

+	/* short mode */

 	if(getflag(FLAG_SHORT))

 		op += 16;

-	(*ops[op])();

-

-	/* experimental */

+	/* cond mode */

+	if(getflag(FLAG_COND)) {

+		if(wspop8())

+			(*ops[op])();

+	} else

+		(*ops[op])();

+	/* devices: experimental */

 	if(cpu.ram.dat[0xfff1])

 		device1(&cpu.ram.dat[0xfff0], &cpu.ram.dat[0xfff1]);

-

 	cpu.counter++;

 	return 1;

 }

@@ -245,7 +243,7 @@ debug(void)

 		getflag(FLAG_HALT) != 0,

 		getflag(FLAG_SHORT) != 0,

 		getflag(FLAG_SIGN) != 0,

-		getflag(FLAG_TRAPS) != 0);

+		getflag(FLAG_COND) != 0);

 }

 int

@@ -32,7 +32,7 @@ Program p;

 char ops[][4] = {

 	"BRK", "LIT", "---", "---", "PEK", "POK", "LDR", "STR",

-	"JMU", "JMC", "JSU", "JSC", "RTU", "RTC", "---", "---",

+	"JMP", "JSR", "RTI", "RTS", "---", "---", "---", "---",

 	"POP", "DUP", "SWP", "OVR", "ROT", "AND", "ORA", "ROL",

 	"ADD", "SUB", "MUL", "DIV", "EQU", "NEQ", "GTH", "LTH"

 };

@@ -103,7 +103,7 @@ findoperator(char *s)

 		while(s[3 + m]) {

 			if(s[3 + m] == '^') i |= (1 << 5); /* mode: 16 bits */

 			if(s[3 + m] == '~') i |= (1 << 6); /* mode: signed */

-			if(s[3 + m] == '&') i |= (1 << 7); /* mode: unused */

+			if(s[3 + m] == '?') i |= (1 << 7); /* mode: conditional */

 			m++;

 		}

 		return i;