A low-voltage operation and highly-reliable nonvoltatile semiconductor memory with a large capacity has been manufactured using 0.8-µm CMOS technology. This 3-volt, 1-Mbit, full-featured MONOS EEPROM has a chip size of 51.3 mm2 and a memory cell size of 23.1µm2. An asymmetric programming voltage method fully exploits the abilities of the MONOS device and provides 10-year data retention after 106 erase/write cycles. Because of its wide-margin circuit design, this EEPROM can also be operated at 5 volts. High-speed read out is provided by using the polycide word line and the differential sense amplifier with a MONOS dummy memory. New functions such as data protection with software and programming-end indication with a toggle bit are added, and chips are TSOP packaged for use in many kinds of portable equipment.

In this paper, the fundamental characteristics of tactile recognition by electrical stimulus in order to develop a vision substitution system were described. The electrical stimulus pulse or DC voltage was applied at a touch board, and a conducting band which was connected to the ground level was fastened around a root of finger. First of all, the resistance of finger by the DC voltage was measured and the equivalent circuit of a finger was estimated. It was found that the most of resistance of this mechanism was concentrated at the contact of tip of finger and its value reached to MΩ order. And this resistance widely varied by the contact condition. The resistance of finger itself was relatively low and the contact resistance of band connectoin was about 30 kΩ. Total stray capacitance was about 26-62 nF, which was calculated by our experiments. Secondly, the minimum recognition voltage to applied stimulus pulse was measured by changing frequency, duty-ratio and voltage of pulse. It was found that the most sensitive pulse was in situation of that the frequency range was within from 60 Hz to 300 Hz, the duty-ratio of 20%, and the minimum sensitive voltage was about 13V. Lastly, this electrical stimulus pulse was applied to the touch Braille board. A touch Braille board was controlled by a computer (PC8801). In this system, an input letter from keyboard is translated to Braille code data by a computer automatically, which express the letter by the 6 points for the brind. And a Braille data is output at a touch board. By touching on the contact point of the touch board, a person can recognize Braille points by electrical stimulus. It was found that the Braille recognition by electrical stimulus pulse was available as same as it could be done by raised points.

Via electromigration (EM) performance of aluminum based metallization (AL) systems has been investigated for vias chains of 1500-4000 vias of 1.0 micron diameter. The results show that via EM lifetime can not be enhanced by a simple increase of M2 step coverage in AL/AL vias because the EM induced voids are formed at AL/AL via interface where electrons flow from Ml to M2 even in the case of very poor M2 step coverage. The voids are induced by the boundary layer in AL/AL vias, where a temperature gradient causes discontinuity of aluminum atoms flux. The failure location is not moved though via EM lifetime can be improved by controlling stress in passivation, sputter etch removal thickness and grain size of the first metal. Next, the effect of the boundary layer are eliminated by depositing titanium under the second aluminum or depositing WSi on the first aluminum. In the both cases, via EM lifetime are improved and the failure locations are changed. Especially WSi layer suppresses the voids formation rather than titanium. Models for the failure mechanism in each metallization system are further discussed.

In this letter, we study on the sensitivity to the electrical stimulus pulse for biomedical electronics for the purpose to make a tactile vision substitution system for binds. We derive the equivalent circuit of finger by measuring sensitive voltages with various touch condition and various DC voltage. And we consider to the sensitivity of finger against electrical stimulus pulse. In order to convert the sense of sight to tactile sense, we consider four types of touch condition and various types of pulse. It is shown that the sensitivity of finger to electrical stimulus pulse is determined by duty-ratio, frequency, hight of pulse and the type of touch condition. In the case that duty-ratio is about 20%, frequency is within about 60-300Hz and touch condition is A-4 type, the sensitive voltage becomes the lowest. With this result, a tactile vision substitution system can be developed and the system will be used to transfer various infomations to blinds without paper.

This paper discusses multiple-valued memory circuit using floating gate devices. It is an object of the paper to provide a new and improved analog memory device, which permits the memory of an amount of charges that accurately corresponds to analog information to be stored.

This paper discusses the conversion of spatial resolution (pixel density) and amplitude resolution (levels of brightness) for multilevel images. A source image is sampled by an image scanner or a video camera, and a converted image is printed by a printer with the capability of higher spatial but lower amplitude resolution than the image input device. In the proposed method, the impulse response of the scanner sensor is modeled to obtain pixel values from the convolution of the impulse and the image signal. Discontinuous areas (edge) of the original image are detected locally according to the impulse model and neighbouring pixel values. The edge route is estimated which gives the pixel values for the output resolutions. Comparison of the proposed method with two conventional methods, reciprocal distance weight interpolation and pixel replication, shows higher edge quality for the proposed method.

The security problems of object-oriented database system are investigated and security level assignment constraints and an access control mechanism based on the multilevel access control security policy are proposed. The proposed mechanism uses the Trusted Computing Base. A unique feature of the mechanism is that security levels are assigned not only to data items (objects), but also to methods and methods are not shown to the users whose security level is lower than that of the methods. And we distinguish between the security level of a variable in a class and that in an instance and distinguish between the level of an object when it is taken by itself and it is taken as a variable or an element of another complex object. All of this realizes the policy of multilevel access control.

An extremely accurate and very wide-band quadrature modulator IC fabricated on a single chip using bipolar technology is presented. The characteristics of this quadrature modulator IC are much superior to conventional ones (modulation phase error and deviation from quadrature is about 1/10), and this IC is applicable to high modulation schemes such as 256 QAM. In this circuit, the phase difference between local signals input to each of two balanced modulators is detected by a phase detector, and a variable phase shifter in the local port is controlled automatically by the detected signals. This, along with the use of a wide-band variable phase shifter, enables the phase difference between the local signals input to the balanced modulators to be adaptively controlled to 90 degrees in wide frequency bands. In addition, a design method for the balanced modulators to obtain small modulation phase error is described. Based on this design method, a highly accurate quadrature modulator IC was fabricated, in which two balanced modulators, the phase detector, and the variable phase shifter were integrated on a single chip. Phase deviation from quadrature in the local signals was reduced to less than 0.3 degrees in the wide frequency bands of more tham 60 MHz. The modulation phase error of the balanced modulators wes less than 0.2 degrees at 140 MHz, and less than 2.5 degrees at up to 1.3 GHz.