Abstract: An adaptable, programmable convolutional interleaving and de-interleaving system uses less space in an integrated circuit than prior art techniques, and is scalable for wide variety of values of I and M. The coder comprises a coder input receiving a stream of data in time with a clock, the stream of data being supplied in units of data such as bytes, and a coder output which supplies the interleaved or de-interleaved data. A single port RAM having an address input, a data input coupled to the coder input, and a data output coupled to the coder output is included. An address generator is coupled with the clock, and supplies a sequence of addresses to the address input in time with the clock. The sequence of addresses implements a convolutional pattern having cells with a depth equal to M units of data and having a number of rows I+1. Each row, based on an index i going from 0 to 1, includes i cells.

Abstract: There is provided herein a joystick interface which includes circuitry to detect when the joystick output signal has been at a steady-state level for a predetermined period of time and upon detection of that condition, the circuitry powers down at least some of the circuitry associated with providing the digital signal representation to the computer. In one particular embodiment of the invention, analog circuitry including a slope detector, makes use of two non-overlapping clocks to sample data and provide it to a comparator. The comparator is used to determine if there has been any change between consecutive or sequential samples, representative of joystick shaft movement. After a predetermined number of comparisons showing no change in either a neutral joystick position or a non-neutral joystick position, the digital circuitry is powered-down to a reduced power operating mode.

Abstract: A switched gain element has an input differential transistor pair and a gain control stage formed of a transistor quad. The four transistors of the transistor quad are connected through respective impedances to a supply voltage. The junction of the impedances and the transistors are connected through further respective transistors to output terminals. The further transistors are switched on by respective control voltages applied to switchable current sources. The same control voltages are applied to the transistor quad. Thus, when first predetermined voltages are applied a first voltage corresponding to the value of two of the impedances is output and when second predetermined voltages are applied a second voltage corresponding to the value of the remaining two impedances is output. The invention may also be applied to a mixer for switching the gain.

Abstract: A comparator used in an enhanced N-WELL pad voltage tracking circuit for high (5 Volts) voltage-tolerant buffers is designed to eliminate current leakage when the input/output is tristated and is being driven externally by a weak voltage source. This is accomplished by comparing the pad voltage supplied from the external source to a reference voltage that is a predetermined amount (VTP) less than the low internal voltage source (VDD). Thus, switchover for tracking of the N-WELL voltage tracks very closely the voltage VDD, reducing the differential voltage between the N-WELL and the pad on the pull-up driver for the system, thereby keeping the driver off and eliminating leakage current. The reference voltage is generated either by a diode voltage drop or by a weak source follower.

Abstract: A tree mixer includes a first differential pair of transistors which divide current from a first current source between the transistors in dependence upon a first differential input signal supplied to first input terminals. Two second differential pairs of transistors have controlled paths which conduct current, divided between the transistors of the differential pair in dependence upon a second differential input signal supplied to second input terminals, dependent upon current passed by a respective transistor of the first pair of transistors, to produce a product signal at output terminals. One or more second current sources provide for the total current passed by the first pair of transistors to be greater than the total current passed by the two second pairs of transistors, for improved linearity without increasing noise. A quadrature phase modulator can include two such mixers with common output circuitry.