Crosstalk problem with shielded cable on 6509.

[6509User]

Hi,
I've got an interesting problem with my 6509 test setup. I have the 6509, an SH100100-Flex cable, and the SCB100 shielded connector block. The problem occurs when I configure one line for output and, on a separate port, configure other lines (adjacent to the output line) for input.
Without the cable connected, when I look at the logic on the input lines, they do not mirror the output. With just the cable connected (i.e. no connector block) the input lines seem to be mirroring (that is, have lots of crosstalk) with the output line. However, when I measure the impedance on the pins it is overload. Finally, of course, with the connector block, I have the exact same issue. Does anyone understand what is happening? How do
I prevent this crosstalk? Do you think the cable is not working correctly?

Thanks!

[Allen H]

Hi 6509User,

Since the input impedance of the 6509 is high, and you don't have any other device driving those inputs, then those lines are essentially floating. In this configuration, those lines a very susceptible to crosstalk. Adding the cable allows the inputs to become AC coupled with the adjacent ouptput lines.

Go ahead and connect an output from your device to the 6509's input lines. Once the lines are being driven either high or low, I suspect that the majority of the crosstalk will go away.