Pins

Pins connect tester actions to DUT terminals. Define physical pins first, then add aliases and headers used by protocols, timing, and generated patterns.

Defining Pins

Declare scalar or vector pins in pins.py:

Pin("porta", width=2)
Pin("portb", width=4)
Pin("reset", reset_action="1")
Pin("clk", reset_action="0")

A vector declaration creates indexed pins such as porta0 and porta1. reset_action defines the model state used when pins are reset.

Aliases

Aliases give one physical pin names appropriate to different protocols:

Alias("clk", "swd_clk", "swdclk", "tclk")
Alias("porta0", "swdio")

Use aliases when the electrical connection is identical. Do not create separate physical pins for alternate functional names.

Pin Headers

Headers define ordered collections used by pattern formats and protocol drivers:

PinHeader("ports", "porta", "portb")
PinHeader("swd", "reset", "swdclk", "swdio")
PinHeader("all", "clk", "reset", "porta", "portb")

Header order is significant because vector-based testers render states in that order. Add a regression test when changing it.

Actions And State

Pattern APIs apply semantic actions such as drive high, drive low, verify high, verify low, high impedance, capture, and overlay. The active tester maps those actions to its symbols. Timing waves determine when drive and compare events occur within a cycle.

Derivatives

Package- or product-specific pins belong in the appropriate DUT derivative. Put only truly shared pins in the parent DUT model. This keeps a package change from silently affecting unrelated devices.

Testing

Test pin widths, indexed names, aliases, header membership and order, reset actions, and tester symbol mappings. A missing alias or reordered header can change every vector while leaving pattern source untouched.