Dajgoro wrote:
For the r/w pin i had the idea with the resistor, but not as simply as putting a resistor and hoping that it will work. I would have a 2 to 1 mux(cpu and dma r/w inputs) that would switch depending who is generating the r/w signal. When the cpu is generating the r/w signal the cpu r/w pin would be connected through a buffer that is then connected to a resistor, and then to the dma r/w. When the dma generates the r/w it would override the cpu's r/w signal since it is coming through a resistor. Soooo what value would suit? What about 1k?
I need to minimize the glue logic to the max, since i have very little free real estate left, the dma, mmu, 4x ram, zif socket for rom, cpu tristate buffers, and bus amplifiers took like 80% of the pcb.
I'm not at all sure I'm following this.
If you're going to have a mux what do you need the resistor for?
If you need the resistor, you better have (dedicated) buffers, so why not
leave out the buffers and resistor and use a mux (assumes you have some
control signal to switch the mux)
If you're going to use CMOS and they're dedicated to to this function,
ie you have a buffered R/W signal that doesn't have to drive anything
but the resistor-buffer then (probably) the smaller the resistor the better
and you could probably get away with something in the hundreds of ohms
range.
twere me, I'd bite the bullet and put in a mux if that's at all feasible (if
you have the signal to control it).
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