AR# 2140: Foundation: Difference between I/O Pads and I/O Terminals
Foundation: Difference between I/O Pads and I/O Terminals
Keywords: ipad opad iopad Terminal
General Description: What is the difference between the I/O terminals found on the toolbar in the Schematic Editor, and the I/O pads found in the Xilinx libraries?
I/O Terminals ------------- These are placed by clicking on the I/O Terminal button on the Toolbar on the left-hand side of the Schematic Editor window.
I/O terminals should ONLY be used in macros to connect signals to the corresponding pins on the macro symbol. They provide the connection between levels of hierarchy in the design.
If an I/O terminal is placed on a top-level schematic, it MIGHT be treated as an I/O pad by the software. But in some cases, the terminal will not be treated as an I/O pad. For this reason, I/O terminals should not be used on any top-level schematic. Signals that span multiple pages of a flat design do not require terminals or off-page connectors.
I/O Pads -------- These are components from the Xilinx Unified Library, and are placed just as you would add components like AND gates, flip-flops, etc. They are called IPAD, OPAD, IOPAD, IPAD4, OPAD4, etc.
These may be used on any level of hierarchy. They represent the actual pins of the Xilinx device. All device pins MUST be represented with I/O Pads, not I/O Terminals.