Mercurial > repos > blastem

changeset 1300:4b893b02444e

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Basic implementation of CSM mode that should handle documented edge cases. Dodesn't handle the weird undocumented edge cases I don't have a good understanding of yet though
author Michael Pavone <pavone@retrodev.com>
date Sat, 25 Mar 2017 15:41:52 -0700
parents da1ffc4026c4
children babff81e4cfd
files ym2612.c ym2612.h
diffstat 2 files changed, 67 insertions(+), 25 deletions(-) [+]
line wrap: on
line diff
--- a/ym2612.c	Sat Mar 25 11:31:43 2017 -0700
+++ b/ym2612.c	Sat Mar 25 15:41:52 2017 -0700
@@ -252,6 +252,39 @@
 #define TIMER_A_MAX 1023
 #define TIMER_B_MAX 255
 
+#define CSM_MODE 0x80
+
+static void keyon(ym_operator *op, ym_channel *channel)
+{
+	//Deal with "infinite" attack rates
+	uint8_t rate = op->rates[PHASE_ATTACK];
+	if (rate) {
+		uint8_t ks = channel->keycode >> op->key_scaling;;
+		rate = rate*2 + ks;
+	}
+	if (rate >= 62) {
+		op->env_phase = PHASE_DECAY;
+		op->envelope = 0;
+	} else {
+		op->env_phase = PHASE_ATTACK;
+	}
+	op->phase_counter = 0;
+}
+
+static const uint8_t keyon_bits[] = {0x10, 0x40, 0x20, 0x80};
+
+static void csm_keyoff(ym2612_context *context)
+{
+	context->csm_keyon = 0;
+	uint8_t changes = 0xF0 ^ context->channels[2].keyon;
+	for (uint8_t op = 2*4, bit = 0; op < 3*4; op++, bit++)
+	{
+		if (changes & keyon_bits[bit]) {
+			context->operators[op].env_phase = PHASE_RELEASE;
+		}
+	}
+}
+
 void ym_run(ym2612_context * context, uint32_t to_cycle)
 {
 	//printf("Running YM2612 from cycle %d to cycle %d\n", context->current_cycle, to_cycle);
@@ -262,6 +295,9 @@
 			if (context->timer_control & BIT_TIMERA_ENABLE) {
 				if (context->timer_a != TIMER_A_MAX) {
 					context->timer_a++;
+					if (context->csm_keyon) {
+						csm_keyoff(context);
+					}
 				} else {
 					if (context->timer_control & BIT_TIMERA_LOAD) {
 						context->timer_control &= ~BIT_TIMERA_LOAD;
@@ -269,6 +305,16 @@
 						context->status |= BIT_STATUS_TIMERA;
 					}
 					context->timer_a = context->timer_a_load;
+					if (!context->csm_keyon && context->ch3_mode == CSM_MODE) {
+						context->csm_keyon = 0xF0;
+						uint8_t changes = 0xF0 ^ context->channels[2].keyon;;
+						for (uint8_t op = 2*4, bit = 0; op < 3*4; op++, bit++)
+						{
+							if (changes & keyon_bits[bit]) {
+								keyon(context->operators + op, context->channels + 2);
+							}
+						}
+					}
 				}
 			}
 			if (!context->sub_timer_b) {
@@ -309,22 +355,12 @@
 				//operator->envelope = operator->sustain_level;
 				operator->env_phase = PHASE_SUSTAIN;
 			}
-			for(;;) {
-				rate = operator->rates[operator->env_phase];
-				if (rate) {
-					uint8_t ks = channel->keycode >> operator->key_scaling;;
-					rate = rate*2 + ks;
-					if (rate > 63) {
-						rate = 63;
-					}
-				}
-				//Deal with "infinite" rates
-				//According to Nemesis this should be handled in key-on instead
-				if (rate >= 62 && operator->env_phase == PHASE_ATTACK) {
-					operator->env_phase = PHASE_DECAY;
-					operator->envelope = 0;
-				} else {
-					break;
+			rate = operator->rates[operator->env_phase];
+			if (rate) {
+				uint8_t ks = channel->keycode >> operator->key_scaling;;
+				rate = rate*2 + ks;
+				if (rate > 63) {
+					rate = 63;
 				}
 			}
 			uint32_t cycle_shift = rate < 0x30 ? ((0x2F - rate) >> 2) : 0;
@@ -727,6 +763,9 @@
 			if (value & BIT_TIMERB_RESET) {
 				context->status &= ~BIT_STATUS_TIMERB;
 			}
+			if (context->ch3_mode == CSM_MODE && (value & 0xC0) != CSM_MODE && context->csm_keyon) {
+				csm_keyoff(context);
+			}
 			context->ch3_mode = value & 0xC0;
 			break;
 		}
@@ -736,19 +775,20 @@
 				if (channel > 2) {
 					channel--;
 				}
-				uint8_t bits[] = {0x10, 0x40, 0x20, 0x80};
+				uint8_t changes = channel == 2 
+					? (value | context->csm_keyon) ^  (context->channels[channel].keyon | context->csm_keyon)
+					: value ^ context->channels[channel].keyon;
+				context->channels[channel].keyon = value & 0xF0;
 				for (uint8_t op = channel * 4, bit = 0; op < (channel + 1) * 4; op++, bit++) {
-					if (value & bits[bit]) {
-						if (context->operators[op].env_phase == PHASE_RELEASE)
-						{
+					if (changes & keyon_bits[bit]) {
+						if (value & keyon_bits[bit]) {
 							first_key_on = 1;
 							//printf("Key On for operator %d in channel %d\n", op, channel);
-							context->operators[op].phase_counter = 0;
-							context->operators[op].env_phase = PHASE_ATTACK;
+							keyon(context->operators + op, context->channels + channel);
+						} else {
+							//printf("Key Off for operator %d in channel %d\n", op, channel);
+							context->operators[op].env_phase = PHASE_RELEASE;
 						}
-					} else {
-						//printf("Key Off for operator %d in channel %d\n", op, channel);
-						context->operators[op].env_phase = PHASE_RELEASE;
 					}
 				}
 			}
--- a/ym2612.h	Sat Mar 25 11:31:43 2017 -0700
+++ b/ym2612.h	Sat Mar 25 15:41:52 2017 -0700
@@ -42,6 +42,7 @@
 	uint8_t  ams;
 	uint8_t  pms;
 	uint8_t  lr;
+	uint8_t  keyon;
 } ym_channel;
 
 typedef struct {
@@ -93,6 +94,7 @@
 	uint8_t     lfo_counter;
 	uint8_t     lfo_am_step;
 	uint8_t     lfo_pm_step;
+	uint8_t     csm_keyon;
 	uint8_t     status;
 	uint8_t     selected_reg;
 	uint8_t     selected_part;