Re: Jeri board and extra things

From: Ruud Baltissen (
Date: 2001-05-03 16:03:58

Hallo David,

> Keep this connected in case you need it for ram refresh or a clock.

Yes, but CLK2 is also used to enable buffers and to latch data. This could
lead to unwanted latching or unwanted output.

> > IMHO. Buffering of outgoing signals can be realized by a 541.
> The 244 can buffer.. Why are you using a latch?

The 541 isn't a latch, but a buffer. The difference with the 244 is that the
inputs are on pin 2-9 and the outputs on pin 11-18. An other difference is
the way it is enabled.

> However, if a cart-port device needs to DMA from/to the I/O region (i.e.
> cart slot), the data bus needs to be disconnected.  So, the game and I/O
> lines must disable the transciever so it doesnt step on the data.  (this
> the challenge stated above)  Is this a working solution?

Looks good.

> Unless you also tweaked the cart port for a single cycle, triggering
> and disabling the ram/rom underneath ;)

To be honnest, I'm not sure if I understood the explanation I got the last
time. Is there a "UltiMax for dummies" available somewhere, please?

Groetjes, Ruud

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