United States Patent [19]
Furuta
[54] SERIAL DATA TRANSMISSIONS DEVICE AND TERMINAL UNIT FOR THE SAME
[75] Inventor: Naofumi Furuta, Tachikawa, Japan
[73] Assignee: Sunx Limited, Tachikawa, Japan
[21] Appl. No.: 283,750
[22] Filed: Aug. 1, 1994
[30] Foreign Application Priority Data
Aug. 3, 1993 [JP] Japan 5-212246
Jun. 14, 1994 [JP] Japan 6-156709
[51] Int. CI.6 H04B 3/46
[52] U.S. CI 375/228; 375/224; 370/14;
340/815.17
[58] Field of Search 375/10; 370/13,
370/14, 15, 16, 16.1, 85.1, 85.15; 455/53.1, 54.2; 340/825.06, 825.07, 825.16, 825.17
[56] References Cited
U.S. PATENT DOCUMENTS
4,149,144 4/1979 Diefenderfer 340/147 R
4,161,635 7/1979 Wolaver 370/15
4,227,181 10/1980 Brittain 340/147 R
4,293,947 10/1981 Brittain 370/85.1
4,586,040 4/1986 Akiba et al 340/825.08
4,679,192 7/1987 Vanbrabant 370/85.1
4,841,520 6/1989 Steely 370/13
FOREIGN PATENT DOCUMENTS 59-62247 4/1984 Japan .
Primary Examiner—Stephen Chin
Assistant Examiner—T. Ghebretinsae
Attorney, Agent, or Firm—Finnegan, Henderson, Farabow,
Garrett and Dunner
[57] ABSTRACT
A serial data transmission device has a master unit, plural terminal units, and an abnormal detection unit connected by a signal line. Each terminal unit has an allocated address. The master unit interchanges data with each one of the plural terminal units in sequence. Each interchange of data with one terminal unit constitutes a cycle. Each terminal unit counts the number of data cycles of the master unit. When a terminal unit detects its assigned cycle number in the total sequence of cycles, a confirmation signal is output to the signal line. The abnormal detection unit determines the presence and location of an abnormality in accordance with the absence of a confirmation signal from a particular terminal.
11 Claims, 9 Drawing Sheets
