The current object-oriented class-based approaches to hardware/software co-analysis/co-design of embedded systems are limited in their abilities to properly capture the structure of individual instances of hardware and software components and their interactions. This paper discusses a methodology to extend a structured objectoriented hardware/software co-design methodology based on the High Order Object-oriented Modeling Technique (HOOMT) to incorporate instance-based object and behavioral models. The instance-based structured object-oriented methodology will enable description of a system's structure based on individual instances of hardware and software components and specification of the interactions among them. In addition, lattices are introduced to specify the concurrent behavior of hardware/software components in a concurrent embedded system. These additions further enhance the method's capability of providing a precise set of specifications that can be understood easily by both hardware and software designers in co-analysis/codesign. The methodology has been applied to the specification of hardware and software of a simulated advanced power grid control system.