Patent ID: 8131900
Filing Date: 2012-03-06
Classification: G06F

Abstract:
1. A bus signal control circuit which is connected between a master device which controls transmission or reception of data and a slave device which stores the data, is connected to the slave device through an address bus and a control signal line, and controls a bus signal transmitted or received through the address bus and the control signal line, comprising: a bus diagnosis line which is directly connected to a bus signal receiving terminal of the slave device without passing through the address bus and the control signal line; a memory control unit which controls writing and reading of data to the slave device according to an instruction from the master device; and a bus signal abnormality processing unit which compares an output bus signal output from the bus signal control circuit to the address bus and the control signal line with a feedback bus signal fed back through the bus diagnosis line to determine the presence/absence of a difference, wherein the memory control unit elongates a bus cycle period of an operation being executed when it is determined in the bus signal abnormality processing unit that the difference is present, and the bus signal abnormality processing unit further comprises: a first bus signal comparing unit which compares an address signal transmitted from the memory control unit with a feedback address signal fed back through the bus diagnosis line to determine whether a difference is present; a second bus signal comparing unit which compares a control signal transmitted from the memory control unit with a feedback control signal fed back through the bus diagnosis line to determine whether a difference is present; and a signal generating circuit which measures a time of a period in which it is determined in one of the first and second bus signal comparing units that a difference is present and generates a difference-present signal Ws when the period in which the difference is present is not less than a response time of the slave device.