Patent ID: 6194991
Filing Date: 2001-02-27
Classification: G07C

Abstract:
A system comprising first and second modules, wherein said first module comprises:a first memory in said second module for initially storing a first code; anda transmitter for transmitting a current transmission from said first module to said second module, the transmission including a first sync code, andsaid second module comprising:a second memory initially providing a plurality of sync memory areas, each of said sync memory areas being adapted to store a sync code and a copy of the first code;a receiver for receiving the current transmission from said first module;identifying means for identifying a first one of said sync memory areas as storing a copy of the first code and a second sync code received from said first module in a first previous transmission;first determining means for determining whether or not the second sync code is usable by determining whether the first code stored in said first memory corresponds to the copy of the first code stored in said first sync memory area;second determining means for, if the second sync code is determined to be usable, determining whether or not said first and second modules are in synchronization based on the first sync code received in the current transmission and the second sync code stored in said first sync memory area,wherein, if the second sync code is determined not to be usable, said identifying means identifies a second one of said sync memory areas as storing a third sync code received from said first module in a second previous transmission, and determining whether or not said first and second modules are in synchronization based on the first sync code received in the current transmission and the third sync code stored in said second sync memory area; andwriting means for, if said first and second modules are determined to be in synchronization, writing the first sync code and another copy of the first code from said first memory in a selected one of said sync memory areas.