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changeset 1291:f17fe0d00626

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Adjust Z80 interrupt pulse duration to match hardware measurements
author Michael Pavone <pavone@retrodev.com>
date Sun, 19 Mar 2017 18:32:49 -0700
parents aa1a8eb5bb2b
children 5905593d6828
files genesis.c
diffstat 1 files changed, 2 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- a/genesis.c	Sun Mar 19 12:54:20 2017 -0700
+++ b/genesis.c	Sun Mar 19 18:32:49 2017 -0700
@@ -21,6 +21,7 @@
 #define MCLKS_PER_YM  7
 #define MCLKS_PER_Z80 15
 #define MCLKS_PER_PSG (MCLKS_PER_Z80*16)
+#define Z80_INT_PULSE_MCLKS 2573 //measured value is ~171.5 Z80 clocks
 #define DEFAULT_SYNC_INTERVAL MCLKS_LINE
 #define DEFAULT_LOWPASS_CUTOFF 3390
 
@@ -108,8 +109,7 @@
 {
 	genesis_context * gen = z_context->system;
 	z_context->int_pulse_start = vdp_next_vint_z80(gen->vdp);
-	//Notes in the Genesis Plus GX code suggest this is asserted for one line
-	z_context->int_pulse_end = z_context->int_pulse_start + MCLKS_LINE;
+	z_context->int_pulse_end = z_context->int_pulse_start + Z80_INT_PULSE_MCLKS;
 }
 
 static void sync_z80(z80_context * z_context, uint32_t mclks)