Patent ID: 7848856

Claim:
A communication system for control of a vehicle engine comprising: a master device; a plurality of slave devices; a communication line commonly connecting said master device and said slave devices for data communication therebetween; and a plurality of control lines individually connecting said master device and said slave devices, said communication system being configured such that a selected one of said slave devices which is applied with a communication permission signal from said master device through a corresponding one of said control lines performs communication with said master device, wherein said master device includes: a first counter counting a first number of data items that has been sent from said master device to said slave device performing communication with said master device; a first comparator comparing said first number with a second number predetermined for said slave device performing communication with said master device, and outputting a first signal when said first and second numbers coincide with each other; a second counter counting a third number of data items that has been sent to said master device from said slave device performing communication with said master device; a second comparator comparing said third number with a predetermined fourth number, and outputting a second signal when said third and fourth numbers coincide with each other; and a switching circuit that changes internal connection thereof such that said communication permission signal is applied to another one of said slave devices which should perform communication with said master device next, when said first and second signals have been outputted from said first and second comparators, respectively; wherein said master device includes a ROM as a memory device for storing both of said second number and said fourth number for each of said slave devices; wherein said master device includes an interruption control circuit configured to integrate a count value of said first counter and a count value of said second counter while said slave devices are applied with said communication permission signal once in succession, and generate an interruption at a later one of a timing at which an integrated value of said count value of said first counter becomes equal to a sum of said second numbers predetermined for said slave devices, and a timing at which an integrated value of said count value of said second counter becomes equal to a sum of said fourth numbers predetermined respectively for said slave devices.