I decided to connect my can device using serial port. I want to know could I use multiple salves with only one object dictionary in master at the same time or I have to use an object dictionary for each of them in master?
I'll be grateful for your responses.
Strictly speaking, each node on a CANopen network will have its own Object Dictionary, in order to be compliant with the standard. But sometimes it is not feasible to implement a full-blown CANopen stack for each node, in which case it is common to implement non-compliant slaves that only have the bare minimum of functionality. See this.
As for master/slave, please note that CANopen is a de-centralized protocol and master/slave has nothing to do with data transmission, nor with the presence of an Object Dictionary. A NMT (network management) master in CANopen is simply a node with the task of supervising other nodes. It sends the NMT start remote node message to put other nodes in operational, and it acts as Heartbeat consumer etc.