System for testing internal nodes
First Claim
1. In an integrated circuit device having internal data and address buses respectively connectable to external data and address buses, and having normally accessible internal nodes addressable by normal addresses from the external address bus, the improvement comprising a test mode means (100, 111, 121) in the integrated circuit device for enabling external access of predetermined and normally inaccessible internal test nodes in the integrated circuit device, said test mode means comprising:
- a test mode decode means (103) responsive to an address from the external address bus for outputting a control signal to set the integrated circuit device in either a normal state or a test mode state, the normal state resulting from the address being one of the normal addresses and the test mode state resulting from the address being a predetermined address for initiating a test mode;
a test mode control register means (105) for storing an address of a predetermined internal test node, said address being obtainable from the external data bus;
a multiplexer means (101) responsive to the control signal for connecting the internal address bus (102) to the external address bus for receiving the normal addresses when in the normal state, and connecting to the test mode control register means for receiving the address of a predetermined internal test node when in the test mode state; and
test node decoder means (111,
121) responsive to the control signal and the address of the predetermined internal test node for enabling the transfer of test data from the predetermined internal test node to the internal data bus, thereby allowing the normally inaccessible test node to be accessible from outside the device.
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Accused Products
Abstract
The testing circuit for testing internal nodes of a device includes storage for storing the test addresses of selected internal nodes in the device. A decoder responds to a test command from a microprocessor for selecting the test addresses from the storage and supplies the test addresses to an address bus in place of other addresses supplied to the address bus. A test decoder responds only to the test addresses on the address bus for enabling the transfer of data between the selected internal nodes in the data bus for testing the selected internal nodes.
57 Citations
16 Claims
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1. In an integrated circuit device having internal data and address buses respectively connectable to external data and address buses, and having normally accessible internal nodes addressable by normal addresses from the external address bus, the improvement comprising a test mode means (100, 111, 121) in the integrated circuit device for enabling external access of predetermined and normally inaccessible internal test nodes in the integrated circuit device, said test mode means comprising:
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a test mode decode means (103) responsive to an address from the external address bus for outputting a control signal to set the integrated circuit device in either a normal state or a test mode state, the normal state resulting from the address being one of the normal addresses and the test mode state resulting from the address being a predetermined address for initiating a test mode; a test mode control register means (105) for storing an address of a predetermined internal test node, said address being obtainable from the external data bus; a multiplexer means (101) responsive to the control signal for connecting the internal address bus (102) to the external address bus for receiving the normal addresses when in the normal state, and connecting to the test mode control register means for receiving the address of a predetermined internal test node when in the test mode state; and test node decoder means (111,
121) responsive to the control signal and the address of the predetermined internal test node for enabling the transfer of test data from the predetermined internal test node to the internal data bus, thereby allowing the normally inaccessible test node to be accessible from outside the device. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A test mode means included in an integrated circuit device for testing internal nodes in the integrated circuit device, said integrated circuit device being in communication with a microprocessor through an internal address bus, an external address bus and a data bus, and having device memory connected to the internal bus for storing data, said test mode means comprising:
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storage means for storing an address of a selected internal test node in the device, said internal test node being other than that of the device memory, and said address of the selected internal test node being obtainable from the external data bus; means responsive to a test command for selecting the address of the selected internal test node stored in the storage means and for supplying said address of the selected internal test node to the internal address bus; and test node decoder means responsive only to the address of the selected internal test node on the internal address bus for enabling the transfer of data between the selected internal test node and the data bus for testing the selected internal test node. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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Specification