MSX HDMI mutlimedia card

Thanks.

I had the same problem with MSX2+, since I do possess none. So far, I've experimented with the machines based on S3527, S1985 and 1990 engines. They all behaved as the spec. But reading the forum, I felt like many in turbo mode experienced the pitch shift of SCC. I was trying to understand why is that.

But Grauw and Manuel precised when it happens. So, any "official" machine should respect the spec and the bus timing therefore.

In my case I use 3.57 slot clock and RESET to synchronize the internal VDP to mine in the cartridge. However, there is no guarantee, that these 3.57 come from the VDP's 21MHz oscillator.

In a future, I should anyway replace the write-only VDP access by full r/w access on a different group of ports (0x88-0x8B). This is also advantageous since there will be no waitstates generated by the MSX engine.

Ha, so the cartridge output clock does not change, but the internal clock to the PSG does. That’s odd!

Fully agree. What I see on A1-ST and also from Hand Otten's schematic pages is that T9769 has no clock output, only the clock input. Also on the first page of A1-WSX there is a pinout of the 6140140 PLA. There we can see two clock inputs from the VDP : DHCLK=10.74MHz and CPUCLK=3.57. And the clock output going to the MSX engine is switchable between CPUCLK & DHCLK/2. And another clock CLK4=3.57MHz going to the SLOT.
As you mentioned, there is an external to the MSX engine circuitry which manages the flipping from one clock to the other. I'm assuming the same and this is done inside that PLA.

One more comment:
DHCLK and CPUCLK are phase synchronized, where one CPUCLK period is exactly 3xDHCLK periods. Then, likely by generating inside PLA the waitstates to MSXENGINE, the required slow timing diagram can be achieved in TURBO mode matching the original Z80 running at 3.57MHz.
Then, possibly, the small timing difference in TURBO vs NONTURBO observed on the MSX SLOT can be compensated inside the PLA by phase shifting the CLK4 output.

So, for the moment, I'll stick to the MSX datapack thing.

BTW, interesting to know how many machines were produced with the native TURBO mode?

Ok +1 assembled.

Count me in too

assembled model one

thanks