ARM Technical Support Knowledge Articles

What is the timing relationship between TDI/SDIN and TDO/SDOUTBS?

Applies to: ARM720T, ARM7TDMI, ARM920/922T, ARM940T, ARM9TDMI

Answer

TDI is fed into a D-type Flip Flop, clocked by the rising edge of TCK. The output of this Flip Flop is presented on SDIN. If one of the user added scan chains is selected, SDOUTBS is fed asynchronously through from the user added scan chain to TDO.

ARM9 Scan Chain

The same applies to the ARM7TDMI, only there SDIN in the above picture is called SDINBS. Data is clocked out of the ARM core and out of each scan chain element on the rising edge of TCK. Data is clocked into a scan chain element at the falling edge of TCK.

See also:

Attachments: img1895.gif

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

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