Abstract: An oscillator with temperature compensation produces a stable clock frequency over wide variations of ambient temperature, and it includes an oscillation generator, two independent current generators, a transition detector and a clock inhibitor. The outputs of the two programmable, independent current generators are combined to provide a capacitor charging current that is independent of temperature. The oscillator is capable of three modes of operation: fast mode, slow/low power mode and sleep mode, which are controlled by the transition detector in response to external control signals. When the transition detector transitions from one mode to another, it controls the clock inhibitor to block a clock output of the oscillator generator for a predetermined number of clock cycles to allow the clock output to stabilize. The oscillator is implemented on a single, monolithic integrated circuit.

Abstract: A precision relaxation oscillator with temperature compensation produces a stable clock frequency over wide variations of ambient temperature. The invention has a oscillation generator and two independent current generators. The outputs of the two programmable, independent current generators are combined to provide a capacitor charging current which is independent of temperature. The precision relaxation oscillator with temperature compensation is implemented on a single, monolithic integrated circuit.

Abstract: A time-based digital temperature sensing system has a first oscillator which is temperature sensitive. The first oscillator has a temperature coefficient which allows the first oscillator to generate an output signal which varies linearly as a function of temperature. A second oscillator is provided and is used to generates a reference clock signal. The outputs from the first and the second oscillator are coupled to a timer. The timer has a clock input coupled to an output of the second oscillator and an enable input coupled to an output of the first oscillator. From these input signals, the timer generates a number indicative of a length of time the timer is enabled by the first oscillator. The number is proportional to a current temperature of a material that is being monitored by the temperature sensing system.

Abstract: Apparatus for providing multiple of discrete voltage levels to drive a liquid crystal display (LCD) from an LCD module on board a microcontroller chip includes a charge pump with a switched-capacitor that develops the discrete voltages as multiples of the value of a base voltage that remains substantially without change irrespective of change in the supply voltage. A switched-capacitor charging circuit selectively charges a capacitor to produce successive additive charges individually retrievable from the capacitor. An LCD drive selectively transmits the discrete voltage levels to activate the LCD according to status of an external system under the control of the microcontroller. Voltage losses that may occur during the switched-capacitor charging are compensated to maintain the levels of the discrete voltages free of decay.

Abstract: A direct sensor interface (DSI) module which allows a microcontroller to directly interface to sensors having at least one of a resistive, capacitive, and/or current source characteristic. The DSI module is coupled directly to a sensor device, which could be a reference resistor, which generates a sensor current. A current mirroring circuit outputs a charging current proportional to the sensor current. A capacitive sensor and/or a capacitive device is coupled to the current mirroring circuit and generates a voltage when charged by the charging current. Using a comparator and a threshold voltage source, the time it takes the capacitive sensor and/or a capacitive device to ramp up from zero to the threshold voltage can be measured. The charging time is proportional to the sensor reading.

Abstract: A microcontroller for use in battery charging and monitoring applications is disclosed. The microcontroller includes a microprocessor and various front-end analog circuitry such as a slope A/D converter and a multiplexer for allowing a plurality of analog input signals to be converted to corresponding digital counts indicative of signal level. The microcontroller also includes an I.sup.2 C interface for supporting a bi-directional two wire bus and data transmission protocol that is useful for serially communicating with other peripheral or microcontroller devices. By making use of the I.sup.2 C interface, the microcontroller can be programmed while in the end application circuit. Such a feature allows customers to manufacture boards with unprogrammed devices and then program the microcontroller just before shipping the product. This allows the most recent firmware or a custom firmware to be programmed.

Abstract: A microcontroller for use in battery charging and monitoring applications is disclosed. The microcontroller includes a microprocessor and various front-end analog circuitry including a slope A/D converter and a multiplexer for allowing a plurality of analog input signals to be converted to corresponding digital counts indicative of signal level. The slope A/D converter includes a digital-to-analog converter (DAC) for providing a programmable charging current to generate a voltage across a capacitor, a precision comparator having inputs for receiving a selected analog input and the capacitor voltage, a counter and a capture register. After a reset is performed, the capacitor is charged while the counter begins counting such that when the capacitor voltage exceeds the selected analog input voltage, the comparator switches logic states thereby causing the obtained count of the counter to be stored in the register.

Abstract: A microcontroller for use in battery charging and monitoring applications is disclosed. The microcontroller includes a microprocessor and various front-end analog circuitry such as a slope A/D converter and a multiplexer for allowing a plurality of analog input signals to be converted to corresponding digital counts indicative of signal level. In order to make the measurements of the selected analog inputs more precise, the microcontroller uses a unique calibration procedure whereby selected parameters associated with the analog circuitry that are subject to variation are measured during test and corresponding calibration constants are calculated therefrom and stored in program memory. These stored calibration constants are subsequently used by the microprocessor in conjunction with the digital counts of the analog input signals for calculating a more precise measurement of the analog input signals.

Abstract: A microcontroller for use in battery charging and monitoring applications is disclosed. The microcontroller includes a microprocessor and various front-end analog circuitry including a slope A/D converter and a multiplexer for allowing a plurality of analog input signals to be converted to corresponding digital counts indicative of signal level. The microcontroller further includes an on-chip temperature sensor, used in conjunction with the A/D converter, to monitor the temperature of the microcontroller. The temperature sensor generates and uses a differential voltage that is obtained across the base-emitter functions of two compatible bipolar transistors having dissimilar emitter areas. This differential voltage is proportional to temperature and may be sampled by the A/D converter to obtain a digital count indicative of the temperature of the microcontroller.

Abstract: A full set of 36 EMS registers is provided for a computer, without using any of the registers located in the 256K to 640K address range of the standard RAM. This is accomplished by providing first and second alternate RAM sets of 12 registers each, which are accessed in the same 768K to 960K space as the standard twelve registers located in the 768K to 960K space. Access to the 24 registers in the first and second alternate sets of registers is controlled by two control bits. These bits translate address signals directed to the 768K to 960K space to be directed to one or the other of the first and second alternate sets of 12 registers; so that the alternate registers are accessed in the same space as the standard 12 registers in this 768K to 960K space.

Abstract: Apparatus for digitally trimming the output frequency of a real-time clock is disclosed. The output frequency of a divider chain is adjusted by the contents of a trim constant register. The amount of correction and direction (slow or fast) to be effected is determined by the trim constant register. During "slow" real-time clock operation, the divider chain "shortens" the next second produced by the real-time clock. During "fast" real-time clock operation, the production of the next second is blocked and then a portion of the "blocked" signal is "added back" to effectively "lengthen" the next second produced by the real-time clock.

Abstract: A circuit generates a system clock signal. On a first input of the circuit a first oscillating signal is placed. On a second input, a second oscillating signal may be placed. Clock sense logic is connected to the second input. The clock sense logic detects whether the second oscillation signal is present on the second input. When the second oscillating signal is not present on the second input, the first oscillating signal is selected to be used to generate the system clock. When the second oscillating signal is present on the second input, the second oscillating signal is selected to be used to generate the system clock. The selected oscillating signal is divided to produce the system clock signal. A first frequency divider divides the selected oscillating signal by a first amount. In parallel, a second frequency divider divides the selected oscillating signal by a second amount.

Abstract: A write protection circuit for the Real Time Clock (RTC) Random Access Memory (RAM) of a computer prevents the writing of data into the RTC RAM in the event of a power supply interruption, including write operations which are in progress during removal or interruption of the power supply. This is accomplished by latching both the address and the data in a buffer instead of connecting the respective address and data buses directly to the destination address location in the RTC RAM. In addition, once the data is buffered, the actual write signal to the internal destination of the RTC RAM is delayed until termination of the write strobe pulse. Once the write strobe pulse is terminated; and, additionally, if no power supply interruption has occurred during the latching of the data, an asynchronous monostable multivibrator generates a delayed write strobe which is used to transfer the latched data to the RTC RAM.