An Interface Control Document is a specification of the Interfaces of a system. In ECSS processes, it is specified by ECSS-E-ST-10-24C ^[1].

Common Types of ICD

Different types of ICD have different expected content, and form.

Mechanical ICD (MICD)

A Mechanical ICD, is usually a technical drawing of the system or sub-system, with a focus on the exterior dimensions, and specifications of the mounting points. It is one of the few documents described by an ECSS standard for which there is no exhaustive description.

Electrical ICD (EICD)

The electrical ICD defines the electrical connections between the sub-system and other sub-systems. This covers physical aspects (the type of connector, the function of each pin, the voltage and current levels on each pin) and logical aspects (nominal/redundant, cross-strapping, ...)

In general, it should include a block-level diagram of the sub-system describing how the different electrical interfaces of the equipment are connected together.

Software ICD

The software ICD describes the logical messages exchanged over the different communications protocols described in the electrical ICD.

For each interface, it will describe the layout of messages (start-of-frame, header, payload, end-of-frame, ...) and the meaning of each field. When the protocol supports multiple types of messages, each message will be described.