Data communication system

A method of controlling writing of communication data in a buffer device and reading of said communication data out of said buffer device in a communication system in which a plurality of time slots are provided, said communication data being arranged in reserved ones of said time slots, and said communication data including control information and being propagated in a communication transmission line, comprising the steps of:

• receiving said communication data from said communication transmission line and writing said communication data in said buffer device at a predetermined write rate;
• starting to read said communication data, written in said buffer device, out of said buffer device at a predetermined read rate;
• detecting positions of said reserved ones of said tome slots based on said control information of said communication data;
• determining a position where the quantity of said communication data accumulated in said buffer device becomes a minimum based on detected positions of said reserved ones of said time slots;
• comparing the quantity of said communication data written and accumulated in said buffer device with a predetermined threshold during the period from a read start point of time until reaching the position where the quantity of data becomes the minimum;
• writing said communication data from said communication transmission line in said buffer device when it is found as a result of comparison that the quantity of said accumulated communication data is the same as or less then said threshold;
• and
• writing said communication data from said communication transmission line and reading said communication data out of said buffer device at the same time when the quantity of said accumulated data is larger than said threshold.

A method of controlling writing of communication data in a buffer device and reading of said communication date out of said buffer device in a communication system in which a plurality of time slots are provided, said communication data being arranged in reserved ones of said time slots, and said communication data including control information and being propagated in a communication transmission line, comprising the steps of:

• receiving said communication data from said communication transmission line and writing said communication data in said buffer device at a predetermined write rate;
• starting to read said communication data, written in said buffer device, out of said buffer device at a predetermined read rate;
• detecting positions of said reserved ones of said time slots based on said control information of said communication data;
• determining a position where the quantity of said communication data accumulated in said buffer device becomes a minimum based on said detected positions of said reserved ones of said time slots;
• not performing read of said communication data out of said buffer device during the period from a read start point of time until reaching the position where the quantity of said communication data becomes the minimum;
• and
• performing both write of said communication data from said communication transmission line and read of said communication data out of said buffer device at and after the position where the quantity of said accumulated data becomes the minimum.

A buffer device arranged between a communication transmission line and a communication terminal equipment in a communication system for controlling transmission of communication data, comprising:

• means for receiving communication data from said communication transmission line;
• memory means for storing received communication data;
• means form controlling timing of writing received communication data in said memory means at a predetermined write rate;
• threshold setting means for designating as a threshold the minimum quantity of communication data accumulated in said memory means;
• and
• means for comparing the quantity of communication data written and accumulated in said memory means with said threshold during a predetermined period from the read start point of time, and prohibiting read of said communication data out of said memory means when the quantity of said accumulated data is the same as or less than said threshold, and permitting read of said communication data out of said memory means at a predetermined read rate when the quantity of said communication data accumulated in said memory means is larger than said threshold.

A communication system having a communication transmission line in which communication data are transmitted and a plurality of communication nodes coupled with said communication transmission line, each of said communication nodes comprising:

• means for receiving data from said communication transmission line;
• communication terminal equipments coupled with said communication nodes;
• a buffer device arranged between said communication receiving means and said communication terminal equipments for controlling transmission of the communication data;
• memory means for storing received communication data;
• memory means for storing received communication data;
• means for controlling timing to write received communication data in said memory means at a predetermined write rate;
• threshold setting means for designating as a threshold the minimum quantity of said communication data accumulated in said memory means;
• and
• means for comparing the quantity of said communication data written and accumulated in said memory means with said threshold for a predetermined period from a read start point of time, and prohibiting read of said communication data out of said memory means when the quantity of said accumulated communication data is the same as or less than said threshold, and permitting read of said communication data out of said memory means at a predetermined read rate when the quantity of said communication data accumulated in said memory means is larger than said threshold.