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author couriersud <couriersud@gmx.org>2019-11-03 23:21:58 +0100
committer couriersud <couriersud@gmx.org>2019-11-03 23:21:58 +0100
commit76ee24ab7ec427e1fc37a716a3ce36fb96322bc9 (patch)
treeb34ed1ffe32ebaea35dac2bf6fbf880a2cbd848b
parent60379b658a0c44fbb6398d122da9464005ea5917 (diff)
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.
-rw-r--r--src/mame/includes/galaga.h4
-rw-r--r--src/mame/video/starfield_05xx.cpp10
2 files changed, 14 insertions, 0 deletions
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
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