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Transparently gathering a chips multiple internal states via scan path and a trigger
| Details |
Inventors: Godfrey, Gary M.; Goodrich, III, Floyd;
Assignee: Advanced Micro Devices Inc. (Sunnyvale, CA)
Primary Examiner: Kim; Kenneth S.
Assistant Examiner:
Attorney, Agent or Firm: Akin Gump Strauss Hauer & Feld LLP
A microcontroller has many miscellaneous logics. The miscellaneous logic can include input/outputs of combinational logic or peripheral devices of the microcontroller, storage devices such as latches, or registers. The miscellaneous logic is coupled to multiple stages of scan cells. The multiple stages can be used as a buffer while the last stage of scan cells are scanned out. A predetermined stage of scan cells are coupled together to form a scan path where data from the miscellaneous logic can be outputted to an external memory. In one embodiment, the predetermined stage is the last stage of scan cells. A trigger signal is used to shift the data from the miscellaneous logic to the next stage of scan cells. Once the last stage of scan cells are loaded, a clocking signal can be provided so that the data in the predetermined stage of scan cells is scanned out. The present invention provides among other things, a graceful way to capture data from miscellaneous logic of the microcontroller using scan hardware. |
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DETAILED DESCRIPTION According to the present invention, a scan path is used to capture data of miscellaneous logic embedded in a microcontroller, such as input/outputs of combinational logic, memory devices such as latches, peripherals in a microcontroller, or a discrete device incorporating scan hardware.
The data is captured in scan cells, such as latches or flip-flops, but the scan cells are implemented in multiple stages.
There can be up to N stages of scan cells, where N is greater than 1.
Each miscellaneous logic is coupled to a corresponding scan cell of a 1st stage; each 1st state scan cell is coupled to a corresponding 2nd stage state scan cell, and so on.
These additional stages of scan cells allow multiple "snapshots" of the scanned logic to be taken without first scanning previous "snapshots".
Each stage of state scan cells can store input/output data of the miscellaneous logic and can eventually be scanned out.
At least the Nth stage of scan cells are serially coupled together to form a scan path.
Should the miscellaneous logic be peripherals embedded in the microcontroller, the scan paths of each peripheral are preferably serially coupled together.
If desired, the scanned information can be used for diagnostics, among other things.
The capturing of data can occur while the microcontroller is running other applications.
It is unnecessary to halt the microcontroller to capture the data.
In addition, the use of multiple stages of scan cells allows the storage of the data should it be impossible to scan the data out as quickly as it is captured.
A trigger can be used to capture the data of the miscellaneous logic into scan cells.
When the scan cells are triggered, the data in the miscellaneous logic are loaded into the 1st stage of state scan cells.
In addition, the states in the 1st stage of scan cells are loaded into the 2nd stage, and so on, up to the Nth stage of scan cells.
The trigger can be initiated under certain criteria.
The criteria can be activation of the trigger by an operator, the happening of an event, the lapse of a predetermined time period, or on other conditions
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I/O Systems 
