ARM Technical Support Knowledge Articles

Is RTCK required as a dedicated output?

Applies to: ARM1026EJ-S, ARM7EJ-S, ARM7TDMI-S, ARM926EJ-S, ARM946E-S, ARM966E-S


For the JTAG interface it is important that the clock synchronization circuit shown in the products Technical Reference Manual is implemented. An example of the ARM9E Family TCK synchronizer is shown below:

ARM9E Family TCK clock synchronizer

ARM9E Family TCK synchronization circuit

It is possible to avoid using the RTCK signal shown in the diagram, however if the RTCK output is not used, it is required that TCK is running at a maximum of 1/6th the system clock frequency if only 1 JTAG synchroniser is implemented in the system.

In the event of more than one clock synchroniser being implemented then the maximum TCK frequency is 1/(6*n) of the slowest processor clock. Where n is the number of synchronisors.

See also:

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Article last edited on: 2008-09-09 15:47:38

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