Telephonic switching system with a user controlled data memory access system and method

In a telephonic switching system having a switch controlled by a central processing unit to interconnect interior communication units with exterior communication units, said central processing unit controls the switch in accordance with communication data in a communication data memory which is alterable in response to signals initiated by said communication units in accordance with an operating system of the central processing unit having a plurality of special processes which share the data, the improvement being a shared data memory access system, comprising:

• means for periodically shifting access to shared data in the data memory successively between the plurality of special processes;
• and
• means for controlling the access shifting means to prevent said access shifting means from shifting access to data memory from one of said plurality of special processes to another one of said plurality of special processes during a period when one of said plurality of special processes with access to the data memory having a data element and another data element is enabled to access shared data including means associated with the operating system to set a flag in the data element of the special process which is enabled to access shared data and means for generating a counted tick value in the other data element of the special process accessing data in response to the periodic access shifting means when the flag is set in the data element of the accessing special process with access.

In a telephonic switching system having a switch controlled by a central processing unit to interconnect communication units in accordance with entry in a data memory including shared data which is alterable in response to signals initiated by said communication units in accordance with an operating system of the central processing unit, the operating system having a plurality of special processes which share at least some of the data, the improvement being a method of controlling access of the special processes to the shared data comprising the steps of:

• normally periodically shifting access to the alterable data memory between said plurality of special processes except when prevented;
• determining when one of said plurality of special processes has access to shared data in said alterable data memory;
• preventing periodic shifting of access away from the one of said plurality of special processes with access during a period when it is determined that shared data is being accessed by the one special process with access;
• and
• stopping the special process accessing data from continuing to access data after a preselected time period.

In a telephonic switching system having a switch controlled by a central processing unit to interconnect communication units in accordance with entry in a data memory including shared data which is alterable in response to signals initiated by said communication units in accordance with an operating system of the central processing unit, the operating system having a plurality of special processes which share at least some of the data, the improvement being a method of controlling access of the special processes to the shared data comprising the steps of:

• normally periodically shifting access to the alterable data memory between said plurality of special processes except when prevented;
• determining when one of said plurality of special processes has access to shared data in said alterable data memory in which the one special process with access has a data element and another data element;
• and
• preventing periodic shifting of access away from the one of plurality of special processes with access during a period when it is determined that shared data is being accessed by the one special process with access by setting a flag in the data element of the special process which is accessing the data and incrementing a counted tick value in the other data element of the special process with access from said data memory in response to each periodic shifting of access to the data memory when the flag is set in the data element of the special process with access.