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JTAG - Configuring multiple devices in a JTAG chain, do you need to buffer the TMS and TCK?
Record #5499
Problem Title:
JTAG - Configuring multiple devices in a JTAG chain, do you need to buffer the TMS and TCK?
Problem Description:
Urgency: Standard
General Description:
Multiple devices in a JTAG chain can reduce the signal quality of the TMS and TCK signals
which are connected in parallel. Is there a design rule of thumb for when to add buffers to
these signals?
Solution 1:
The answer is dependent on many things. Specifically, the environment, and the cable.
The experimental rule of thumb is that after five devices, the signals should run through a buffer.
However, under noisy circumstances, buffers may be needed when using less than 3 devices.
The LS244 is an example of a buffer that has been used successfully with our devices.
End of Record #5499 - Last Modified: 01/07/00 13:18 |
