git.y1.nz

commit 96f4b2c7f77cb9f464dbd6e893ace645f6a11c3f
parent ceb9681fba8340505365d0a8ab6f0409732d3400
Author: Toxa <untoxa@mail.ru>
Date:   Mon, 25 Mar 2024 14:30:59 +0300

SMS/GG/MSX DIV_REG emulation for the Z80 systems, may be useful for seeding RNG

Diffstat:
M
gbdk-lib/include/msx/msx.h
9
+++++++++
M
gbdk-lib/include/sms/sms.h
10
++++++++++
A
gbdk-lib/libc/targets/z80/get_r_reg.s
10
++++++++++
M
gbdk-lib/libc/targets/z80/gg/Makefile
2
+-
M
gbdk-lib/libc/targets/z80/msxdos/Makefile
2
+-
M
gbdk-lib/libc/targets/z80/sms/Makefile
2
+-

6 files changed, 32 insertions(+), 3 deletions(-)
diff --git a/gbdk-lib/include/msx/msx.h b/gbdk-lib/include/msx/msx.h
@@ -315,6 +315,15 @@ void refresh_OAM(void);
 */
 extern volatile uint16_t sys_time;
 
+/** Return R register for the DIV_REG emulation 
+
+    Increments once per CPU instruction (fetches the Z80 CPU R register)
+
+*/
+uint8_t get_r_reg(void) PRESERVES_REGS(b, c, d, e, h, l, iyh, iyl);
+
+#define DIV_REG get_r_reg()
+
 /** Tracks current active ROM bank in frame 1
 */
 extern volatile uint8_t _current_bank;
diff --git a/gbdk-lib/include/sms/sms.h b/gbdk-lib/include/sms/sms.h
@@ -322,6 +322,16 @@ void refresh_OAM(void);
 */
 extern volatile uint16_t sys_time;
 
+
+/** Return R register for the DIV_REG emulation 
+
+    Increments once per CPU instruction (fetches the Z80 CPU R register)
+
+*/
+uint8_t get_r_reg(void) PRESERVES_REGS(b, c, d, e, h, l, iyh, iyl);
+
+#define DIV_REG get_r_reg()
+
 /** Tracks current active ROM bank in frame 1
 */
 #define _current_bank MAP_FRAME1
diff --git a/gbdk-lib/libc/targets/z80/get_r_reg.s b/gbdk-lib/libc/targets/z80/get_r_reg.s
@@ -0,0 +1,10 @@
+	.include	"global.s"
+
+	.title	"DIV_REG emulation"
+	.module	DIV_REG_emu
+
+	.area	_HOME
+
+_get_r_reg::
+	LD	A, R
+	RET
diff --git a/gbdk-lib/libc/targets/z80/gg/Makefile b/gbdk-lib/libc/targets/z80/gg/Makefile
@@ -24,7 +24,7 @@ ASSRC =	set_interrupts.s \
 	palette.s set_palette.s \
 	pad.s pad_ex.s \
 	sms_int.s nmi.s \
-	mode.s clock.s \
+	mode.s clock.s get_r_reg.s \
 	delay.s \
 	emu_debug_printf.s \
 	memset_small.s \
diff --git a/gbdk-lib/libc/targets/z80/msxdos/Makefile b/gbdk-lib/libc/targets/z80/msxdos/Makefile
@@ -18,7 +18,7 @@ ASSRC =	set_interrupts.s \
 	msx_metasprites.s msx_metasprites_hide.s msx_metasprites_hide_spr.s \
 	pad.s \
 	msx_int.s \
-	mode.s clock.s \
+	mode.s clock.s get_r_reg.s \
 	delay.s \
 	memset_small.s \
 	far_ptr.s \
diff --git a/gbdk-lib/libc/targets/z80/sms/Makefile b/gbdk-lib/libc/targets/z80/sms/Makefile
@@ -24,7 +24,7 @@ ASSRC =	set_interrupts.s \
 	palette.s set_palette.s \
 	pad.s pad_ex.s \
 	sms_int.s nmi.s \
-	mode.s clock.s \
+	mode.s clock.s get_r_reg.s \
 	delay.s \
 	emu_debug_printf.s \
 	memset_small.s \

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