Patent ID: 7808917
Filing Date: 2010-10-05
Classification: H04L

Abstract:
1. A system for transmitting telegrams, comprising: at least one first communication device comprising a first counter for sending a telegram; at least one second communication device comprising a second counter for receiving the telegram, wherein the first and second counters comprise a count value which is reset to a reset value upon the start of a transmission sequence between the at least one first and the at least one second communication devices, the count value represented as a plurality of bits comprising higher bits and a lowest bit; wherein the at least one first communication device is adapted to construct and transmit the telegram having process data and a failsafe component, the failsafe component having (a) a first data section comprising failsafe data; (b) a second data section comprising a reset bit having two possible values wherein the reset bit is set to a first value upon the start of the transmission sequence and wherein if an error is detected the reset bit is set to a second value, and wherein if an acknowledgement is received the reset bit is set to the first value; (c) a third data section comprising a count bit having two possible values representing the lowest bit of the count value which toggles upon each increment of the count value in accordance with the transmission sequence; and (d) a fourth section comprising a check value used in error detection; wherein the at least one first communication device increments the count value if the reset bit is set to the first value and resets the count value to the reset value if the reset bit has been set to the first value after having been set to the second value; and wherein the at least one second communication device is adapted to receive the telegram and if the reset bit equals the first value, read the process data of the telegram and increment the count value; and if the reset bit equals the second value, read the failsafe data of the telegram and reset the count value to the reset value.