Networked open and closed loop systems that use Programmable Logic Controllers (PLC) play an important role in recent manufacturing. PLC-based networked automation and control systems (PLC-based NAS/NCS) constitute a well-known category of industrial automation and control systems that use time-based execution platforms. In this dissertation, unified formal modeling and control design of PLC-based NAS/NCS is presented. In the modeling phase a two-step approach is used. First, a structure-conserving Colored Petri Nets (CPN) model for the whole NAS/NCS is built and simulated to generate extensive time-stamped delay data records. Second, Markov modeling is used in the area of response time estimation in case of NAS. In the control phase for NCS, mutual Markov modeling is used with Markovian Jump Linear System (MJLS) approach to design a new state feedback control.