Data processing: structural design – modeling – simulation – and em – Emulation – In-circuit emulator
Reexamination Certificate
1998-05-22
2001-07-31
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Emulation
In-circuit emulator
C716S030000
Reexamination Certificate
active
06269328
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a testing integrated circuit device, and in particular, to a testing integrated circuit device which is installed on a circuit board in place of an integrated circuit device and is used for simulating the integrated circuit device in order to evaluate EMI noise, crosstalk, etc. of the circuit board on which the integrated circuit device will be installed.
DESCRIPTION OF THE RELATED ART
These days, the operating frequency of electronic devices is being made higher and higher, and according to the high speed operation, high-frequency noise emitted from electronic devices (hereafter referred to as EMI (Electro Magnetic Interference) noise) has become a problem which can not be neglected. The EMI noise is generated and emitted from almost all electronic devices. Therefore, efforts are being made by electronic device manufacturers to lower the EMI noise and bring it within specifications, by providing electromagnetic shielding to the electronic devices, frequency modulating the clock signals which are supplied to the electronic devices, etc.
FIG. 1
is a block diagram showing an example of a conventional method for preventing the EMI noise. Referring to
FIG. 1
, the frequency modulator modulates a clock signal which is supplied from the clock oscillator as shown in FIG.
2
and supplies the frequency modulated clock signal to the integrated circuit device. The frequency of the frequency modulated clock signal is varied periodically between the higher frequency A and the lower frequency B, thereby the absolute value of harmonics occurring in the integrated circuit device is reduced and the EMI noise emitted from the integrated circuit device is reduced.
At present, various kinds of LSIs (integrated circuit devices) are installed on a circuit board. However, users of the LSIs can not perform evaluation of the circuit board on which an LSI is installed, before the particular LSI is actually installed on the circuit board. In the evaluation of circuit boards, the EMI noise, crosstalk between lines on the circuit board, etc. are evaluated. For example, two signals which are simultaneously outputted from the LSI are supplied to two lines which are placed nearby on the user board, and interference between the two lines at a desired distance from the LSI is evaluated by checking signal waveforms.
However the above countermeasures against the EMI noise presently taken by electronic device manufacturers have the following drawbacks.
(1) Extra parts for frequency modulation are necessary and thus the prices of the integrated circuit devices get higher.
(2) EMI noise can be prevented by means of the frequency modulation, however it is difficult to take full advantage of performance of each parts of the integrated circuit device.
(3) EMI noise emitted from an electronic device can be prevented by means of electromagnetic shielding of the electronic device etc., however the EMI noise evaluation and the electromagnetic shielding can be done only after obtaining the LSI (integrated circuit device) which is the source of the EMI noise.
SUMMARY OF THE INVENTION
It is therefore the primary object of the present invention to provide a testing integrated circuit device which is installed on a circuit board in place of an LSI (or an integrated circuit device) in order to simulate the LSI before the LSI is produced or obtained, by which it is made possible to evaluate the EMI noise, crosstalk, etc. of the circuit board on which the LSI will be installed, and to determine appropriate terminal arrangement, driving ability, output signal frequency, etc. of external terminals of the LSI.
In accordance with a first aspect of the present invention, there is provided a testing integrated circuit device comprising a plurality of external terminals for being connected to a circuit board, a plurality of internal terminals provided corresponding to the external terminals each of which is provided with a plurality of connection terminals including a signal terminal, and a plurality of signal terminal setting means provided corresponding to the internal terminals for setting characteristics of the signal terminals. The connection terminals are provided so that a desired one of the connection terminals in the internal terminal can be connected to the corresponding external terminal. Each of the signal terminal setting means includes an input/output setting means for arbitrarily setting whether the signal terminal is an input terminal or an output terminal, an output driving ability setting means for arbitrarily setting output driving ability of the signal terminal, and an output signal frequency setting means for arbitrarily setting the frequency of an output signal of the signal terminal.
In accordance with a second aspect of the present invention, in the first aspect, the connection terminals of each of the internal terminals further include a power terminal for supplying power which is supplied from the circuit board to the testing integrated circuit device, and a ground terminal for connecting the ground of the testing integrated circuit device to the ground of the circuit board.
In accordance with a third aspect of the present invention, in the first aspect, the output signal frequency setting means includes a frequency multiplier/demultiplier for multiplying/demultiplying a clock signal supplied from the circuit board, and a third control circuit for setting the multiplying/demultiplying number of the frequency multiplier/demultiplier according to a signal which is supplied from outside the testing integrated circuit device. The output driving ability setting means includes a plurality of constant current sources each of which varies its output current according to the output of the frequency multiplier/demultiplier, and a second control circuit for selecting one or more constant current sources out of the constant current sources in the output driving ability setting means according to a signal which is supplied from outside the testing integrated circuit device and enabling the selected constant current sources to output signals to the signal terminal. And the input/output setting means includes a first control circuit which is provided with a function for totally disabling the constant current sources from outputting signals to the signal terminal according to a signal which is supplied from outside the testing integrated circuit device.
In accordance with a fourth aspect of the present invention, in the third aspect, the second control circuit sets the output driving ability of the signal terminal by varying the number of the selected constant current sources.
In accordance with a fifth aspect of the present invention, in the third aspect, the constant current sources are provided with different values of driving abilities, and the second control circuit sets the output driving ability of the signal terminal by selecting one constant current source according to the signal which is supplied from outside the testing integrated circuit device.
In accordance with a sixth aspect of the present invention, in the third aspect, the first control circuit and the second control circuit are realized by a logic decoder circuit for decoding data of a register which is set by the signal supplied from outside the testing integrated circuit device.
In accordance with a seventh aspect of the present invention, in the third aspect, the signal terminal setting means includes one or more registers provided to the first, second and the third control circuits, whose data are set by the signal supplied from outside the testing integrated circuit device. The registers provided to all of the signal terminal setting means are connected in series to form a shift register, and the operation of the first, second and the third control circuits is determined by setting the data of the registers by supplying the shift register with a serial signal as the signal supplied from outside the testing integrated circuit device.
In accordance with an eighth aspect of the present invent
Jones Hugh
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Teska Kevin J.
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