From 76ee24ab7ec427e1fc37a716a3ce36fb96322bc9 Mon Sep 17 00:00:00 2001 From: couriersud Date: Sun, 3 Nov 2019 23:21:58 +0100 Subject: [PATCH] Galaga: small fix and some notes. [Couriersud] - leave some more information about the equivalent galois LFSR like taps and seed values. - All members are now initialized by constructor. --- src/mame/includes/galaga.h | 4 ++++ src/mame/video/starfield_05xx.cpp | 10 ++++++++++ 2 files changed, 14 insertions(+) diff --git a/src/mame/includes/galaga.h b/src/mame/includes/galaga.h index 013966950e2..e9311f53a93 100644 --- a/src/mame/includes/galaga.h +++ b/src/mame/includes/galaga.h @@ -34,6 +34,10 @@ public: , m_palette(*this, "palette") , m_leds(*this, "led%u", 0U) , m_starfield(*this, "starfield") + , m_galaga_gfxbank(0) + , m_main_irq_mask(0) + , m_sub_irq_mask(0) + , m_sub2_nmi_mask(0) { } DECLARE_READ8_MEMBER(bosco_dsw_r); diff --git a/src/mame/video/starfield_05xx.cpp b/src/mame/video/starfield_05xx.cpp index 23c349eae33..8a0ec025256 100644 --- a/src/mame/video/starfield_05xx.cpp +++ b/src/mame/video/starfield_05xx.cpp @@ -288,6 +288,16 @@ the Fibonacci form, which is why the latter is used in this implementation. + The LFSR used by Wolfgang and Jindřich had taps at 15, 12, 10 and 5. + With the same seed values, the following holds true: + + Decode_W(lfsr[t-4]) = Decode_J(lfsr[t]) + + The two decoding algorithm (Wolfgang, Jindřich) thus delivered the + same results but with a 4 clock difference. + + Jindřich: Seed Value 0x70cc + Wolfgang: Seed Value 0xe7bf ---------------------------------------------------------------------------