Description of the IORO input/output signals.
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+Next to the supply/ground signals the block has three external signals:
+
+* ro_de: this is connect to the de signal of all 5 IOPadOut IO pad cells so they can all be put in high impedance state
+* ro_en: this signal allows to enable/disable the oscilation of the RO. This signal is connected to a NAND2 gate, the other input is connected to the s signal of the first IOPadIn cell, the output of the NAND2 is connected the the d signal of the last IOPadOut cell.
+* ro_out: this is the buffered output of the RO. It is the output of a buf_x4 cell with the input the s signal of the first IOPadIn cell.
+
## Source
The top level is fully generated from python code in the `doitcode` subdirectory. pydoit is used to generate the desig with the provided `dodo.py` file in the top directory. The code depends on some external modules that are assumed to be installed:
