Monitor Configuration And Token Control Mechanism in a Ring Structured Communication System
Original Publication Date: 1980-Nov-01
Included in the Prior Art Database: 2005-Feb-14
In a ring communication System, as shown schematically above, there are provided several ordinary stations S1...S5 and two stations M1 and M2 which have, besides their normal data station functions, additional monitor capabilities. Though a single monitor would be sufficient for checking, etc., reliability is increased by the second monitor. Access to the ring is controlled by a token mechanism: A circulating free token is converted to busy by the next station ready to send, which station thereafter transmits its message and finally releases a free token again. A method is suggested for replacing a permanently busy token, or a lost token by a monitor, even though two equal and independent monitors are provided. The method also enables the two monitor stations to mutually check their correct operation.