mamedev
circus charlie (arcade): sprites shown one frame in advanced
MAME version
0.268
System information
N/A
INI configuration details
N/A
Emulated system/software
circus charlie
Incorrect behaviour
sprites are directly displayed off sprite memory, bypassing the frame buffer present on the real board.
Although MAME driver captures the existence of a m_spritebank, it is not interpreting it correctly. The CPU selects which part of the sprite memory will be rendered to the frame buffer.
This is the schematic region where the 64 kByte frame buffer is visible. Notice the complex 4-input multiplexer driving it. The top signal is 1V*, which toggles every frame as the name suggests.
This is probably a trivial change in the driver, but it goes beyond my skill. Let me collaborate by simply reporting it.
Expected behaviour
Sprite data should be buffered one frame before rendered
Steps to reproduce
normally run the driver
Additional details
No response
You are absolutely right. The 256V signal below that one toggles every frame.
Driver has no video timing hooked up, do you have that information? Don't think buffered_spriteram will work as intended without that as well.
Circus Charlie, like most Konami games of this era, used an ASIC to generate the H/V timing chain. I don't know the actual timings here, but suspect them to be once again similar to Galaxian/Scramble (16 kHz horizontal, 60.60606 Hz vertical).
It is like Kicker and the others. These are direct measurements off the PCB.
Horizontal period
Vertical period
Frame rate is 60.58Hz, the oscilloscope does not show the second digit.
I added buffered spriteram here: https://github.com/mamedev/mame/commit/36d8b4cabd980653214fe8925ed267b8edecf831
