hi
Kai,

Indeed we use grounded wires between signal lines. In fact, our FRC connection has two 8-bit channels, and it is the one-side directioned. One channel is used as data bus, second one as the address of destination IC (4 bits -> up to 16 ICs) and as slave boards` selectors (rest 4 bits without demux -> 4 boards). At main board it is connected to ULN2803 outputs (open drain), at slave boards it is accepted with 74ALS573`s. All RFC signal lines are pull-upped to +5V with 4k7 resistors on each slave board. First time we thought about lesser pull up value (~470 ohms). But the max. rate of data transfer is no more than 3kHz and so we tested it and found that it does not need to increase the current over FRC. 74ALS573 accepts about 20uA at high input level, so 20x16=320uA and 320uA*4k7=1.5V and 5-1.5=3.5V - it should be enough for correct detection of input logic "1".

Yes, we tested it with 74ALS574 and it has worked as well. But usage of 574 increases a risk to lock wrong data due it has edge-sensetive latch (IMHO). So we keep to use 573 chips.

Regards,
Oleg