Patent ID: 8041747

Claim:
A communication apparatus that detects a memory area that stores data to be transmitted from a memory unit having memory areas defined by IDs (identifier numbers) allotted to the data, and transmits the data extracted by detecting the memory area, the communication apparatus comprising: a plurality of first flags, wherein one of the first flags is provided for each of the memory areas of the memory unit, and indicates whether data in each corresponding memory area is updated; a second flag that is provided for each of a plurality of groups, each group consisting of a predetermined number of the first flags, and indicates a data update status when at least one set of data represented by one of the first flags in the corresponding group is in an updated state; a flag memory part that stores the first flags and the second flag; a flag update processing part that detects an area in the flag memory part that stores the corresponding first flags and the second flag under the condition that the memory unit stores the data to be transmitted, updates a status of each of the first flags in the detected memory area, and updates a status of the second flag in the detected memory area under the condition that the status of the second flag needs to be updated; a data search processing part that executes a search process extracting the data to be transmitted from the memory area by searching for the corresponding first flags after detecting the second flag, and sets the data to be transmitted in a message box; and a transmission processing part that transmits the data set in the message box; wherein: the data search processing part executes the search process at a predetermined cycle and does not execute the search process if there is not a space area in the message box to store the data to be transmitted; the memory area in the flag memory part storing the first flags is formed in a matrix; a number of columns of the matrix is a number of the form 2 n (where n is an integer); and the flag update processing part detects the area in the flag memory part by using an ID shown by a binary number allotted to the data to be transmitted that indicates the area in the flag memory part that stores the first flags and the second flag.