From 0182b489b68d3eae9f38757008ceff1dd5f18b07 Mon Sep 17 00:00:00 2001 From: Paul Swan Date: Wed, 18 Dec 2024 19:46:09 -0800 Subject: misc/cvs.cpp: Add documentation in comments about the effects of the sound registers observed by poking values on a real CVS PCB. (#13099) --- src/mame/misc/cvs.cpp | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/src/mame/misc/cvs.cpp b/src/mame/misc/cvs.cpp index 70b47fca7c3..b598ac3799c 100644 --- a/src/mame/misc/cvs.cpp +++ b/src/mame/misc/cvs.cpp @@ -682,6 +682,25 @@ void cvs_state::sh_trigger_w(offs_t offset, u8 data) // offset 2 is used in darkwar, spacefrt, 8ball, dazzler, superbik, raiders // offset 3 is used in cosmos, darkwar, superbik, raiders + /********** + Additional notes from poking the CVS sound hardware with an + In Circuit Emulator from PrSwan (Paul Swan). + I have recordings available. + + - 0x1884 - Enables an XP8038 frequency generator IC + Reflected on pin 10 of a 4016. + The frequency is set by 0x1840, the 8 bit DAC register. + Not all 0x1840 values were tested, but: + 0x00 - off, 0x1884 enable has no sound. + 0x55,0xAA,0xFF - increasing value has higher frequency + - 0x1885 - A scope showed this halving the XP8038 amplitude with a little decay. + Causes 4016 pin 11 to rise (on) and decay-fall (off) + - 0x1886 - Mikes comment above about a high pitched whistle didn't match my PCBs. His was faulty? + Outputs a complete Galaxia-style ship fire sound, with attack-to-on and decay-to-off. + - 0x1887 - Reflected on an LM380. + Causes an envelope-like operation on the XP8038 tone with attack (on) and decay (off). + ***********/ + data &= 1; if (data != m_sh_trigger[offset]) -- cgit v1.2.3