From 835122bc0c583a74707847f350349e6050b42bb5 Mon Sep 17 00:00:00 2001
From: notaz <notasas@gmail.com>
Date: Sat, 31 Aug 2013 02:23:57 +0300
Subject: [PATCH] sms: add pause support

---
 cpu/DrZ80/drz80.h |  2 +-
 cpu/DrZ80/drz80.s | 37 +++++++++++++++++++++++++++++++++++--
 pico/pico_int.h   |  7 ++++++-
 pico/sms.c        |  7 ++++++-
 4 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/cpu/DrZ80/drz80.h b/cpu/DrZ80/drz80.h
index 708f0a9..05773f9 100644
--- a/cpu/DrZ80/drz80.h
+++ b/cpu/DrZ80/drz80.h
@@ -52,7 +52,7 @@ struct DrZ80
   int cycles;		            /*0x44 - Cycles pending to be executed yet */
   int previouspc;	            /*0x48 - Previous PC */
   unsigned char Z80_IRQ;        /*0x4C - Set IRQ Number (must be halfword aligned) */   
-  unsigned char Z80IF;          /*0x4D - Interrupt Flags:  bit1=_IFF1, bit2=_IFF2, bit3=_HALT */
+  unsigned char Z80IF;          /*0x4D - Interrupt Flags:  bit0=_IFF1, bit1=_IFF2, bit2=_HALT, b3=NMI */
   unsigned char Z80IM;          /*0x4E - Set IRQ Mode */
   unsigned char spare;          /*0x4F - N/A */
   unsigned int z80irqvector;    /*0x50 - Set IRQ Vector i.e. 0xFF=RST */
diff --git a/cpu/DrZ80/drz80.s b/cpu/DrZ80/drz80.s
index edb29df..ff2a6b8 100644
--- a/cpu/DrZ80/drz80.s
+++ b/cpu/DrZ80/drz80.s
@@ -97,6 +97,7 @@ DrZ80Ver: .long 0x0001
 	.equ Z80_IF1, 1<<0
 	.equ Z80_IF2, 1<<1
 	.equ Z80_HALT, 1<<2
+	.equ Z80_NMI, 1<<3
 
 ;@---------------------------------------
 
@@ -1359,9 +1360,11 @@ DrZ80Run:
 
 .if INTERRUPT_MODE == 0
 	;@ check ints
+	tst r0,#(Z80_NMI<<8)
+	blne DoNMI
 	tst r0,#0xff
 	movne r0,r0,lsr #8
-	tstne r0,#1
+	tstne r0,#Z80_IF1
 	blne DoInterrupt
 .endif
 
@@ -1515,6 +1518,36 @@ DoInterrupt_end:
 	ldmfd sp!,{pc} ;@ return
 .endif
 
+DoNMI:
+	stmfd sp!,{lr}
+
+	bic r0,r0,#((Z80_NMI|Z80_HALT|Z80_IF1)<<8)
+	strh r0,[cpucontext,#z80irq] @ 0x4C, irq and IFF bits
+
+	;@ push pc on stack
+	ldr r0,[cpucontext,#z80pc_base]
+	sub r2,z80pc,r0
+	opPUSHareg r2
+
+	;@ read new pc from vector address
+.if UPDATE_CONTEXT
+	str z80pc,[cpucontext,#z80pc_pointer]
+.endif
+	mov r0,#0x66
+.if DRZ80_XMAP
+	rebasepc
+.else
+	stmfd sp!,{r3,r12}
+	mov lr,pc
+	ldr pc,[cpucontext,#z80_rebasePC] ;@ r0=new pc - external function sets z80pc_base and returns new z80pc in r0
+	ldmfd sp!,{r3,r12}
+	mov z80pc,r0	
+.endif
+	ldrh r0,[cpucontext,#z80irq] @ 0x4C, irq and IFF bits
+	eatcycles 11
+	ldmfd sp!,{pc}
+
+
 .data
 .align 4
 
@@ -5615,7 +5648,7 @@ ei_return:
 	;@ check ints
 	tst r0,#0xff
 	movne r0,r0,lsr #8
-	tstne r0,#1
+	tstne r0,#Z80_IF1
 	blne DoInterrupt
 
 	;@ continue
diff --git a/pico/pico_int.h b/pico/pico_int.h
index 690c233..1acc1b0 100644
--- a/pico/pico_int.h
+++ b/pico/pico_int.h
@@ -174,6 +174,8 @@ extern struct DrZ80 drZ80;
 #define z80_run(cycles)    ((cycles) - DrZ80Run(&drZ80, cycles))
 #define z80_run_nr(cycles) DrZ80Run(&drZ80, cycles)
 #define z80_int()          drZ80.Z80_IRQ = 1
+#define z80_int()          drZ80.Z80_IRQ = 1
+#define z80_nmi()          drZ80.Z80IF |= 8
 
 #define z80_cyclesLeft     drZ80.cycles
 #define z80_pc()           (drZ80.Z80PC - drZ80.Z80PC_BASE)
@@ -184,6 +186,7 @@ extern struct DrZ80 drZ80;
 #define z80_run(cycles)    Cz80_Exec(&CZ80, cycles)
 #define z80_run_nr(cycles) Cz80_Exec(&CZ80, cycles)
 #define z80_int()          Cz80_Set_IRQ(&CZ80, 0, HOLD_LINE)
+#define z80_nmi()          Cz80_Set_IRQ(&CZ80, IRQ_LINE_NMI, 0)
 
 #define z80_cyclesLeft     (CZ80.ICount - CZ80.ExtraCycles)
 #define z80_pc()           Cz80_Get_Reg(&CZ80, CZ80_PC)
@@ -193,6 +196,7 @@ extern struct DrZ80 drZ80;
 #define z80_run(cycles)    (cycles)
 #define z80_run_nr(cycles)
 #define z80_int()
+#define z80_nmi()
 
 #endif
 
@@ -313,7 +317,8 @@ struct PicoMS
 {
   unsigned char carthw[0x10];
   unsigned char io_ctl;
-  unsigned char pad[0x4f];
+  unsigned char nmi_state;
+  unsigned char pad[0x4e];
 };
 
 // some assembly stuff depend on these, do not touch!
diff --git a/pico/sms.c b/pico/sms.c
index 58905bd..8c44d51 100644
--- a/pico/sms.c
+++ b/pico/sms.c
@@ -11,7 +11,6 @@
  * - remaining status flags (OVR/COL)
  * - RAM support in mapper
  * - region support
- * - Pause button (NMI)
  * - SN76496 DAC-like usage
  * - H counter
  */
@@ -256,8 +255,14 @@ void PicoFrameMS(void)
   int skip = PicoSkipFrame;
   int lines_vis = 192;
   int hint; // Hint counter
+  int nmi;
   int y;
 
+  nmi = (PicoPad[0] >> 7) & 1;
+  if (!Pico.ms.nmi_state && nmi)
+    z80_nmi();
+  Pico.ms.nmi_state = nmi;
+
   PicoFrameStartMode4();
   hint = pv->reg[0x0a];
 
-- 
2.39.2