Abstract:
The invention provides a particular construction for digital filters in which, instead of multiplying various ones of the digital samples by weights and adding the results together, one or more of the digital samples is inspected by a ranging unit, which then instructs an incrementing unit to increment, decrement or leave alone one of the samples to provide the result. In order to achieve very high data rates, the incremented and decremented values can be pre-prepared whilst the ranging unit makes its decision, and then a multiplexer responsive to the output of the ranging unit is used to select the appropriate one of the pre-prepared values.
Abstract:
A loopback circuit connecting the output of a receiver section to a transmitter section of a transceiver circuit has two or more loopback channels. In this way, the data rate is reduced, reducing the signal loss that occurs even over such short distances at very high data rates.
Abstract:
A control slew rate output driver has a plurality of component drivers that are switched on in turn to provide an edge on the output. A control circuit provides a series of respective control signals component drivers, which are correspondingly switched on in turn. The control circuit takes a signal, preferably a data signal, and supplies it in parallel to a plurality of delay buffers, which delay the data signal by different amounts to produce the control signals for the component drivers. The delay buffers are voltage controlled and the control voltage for each is provided by a respective tap of a voltage divider. The current passes through the voltage divider can be changed to change the control voltages and, hence, the overall rise or fall time provided by the output driver.
Abstract:
A multifunction access circuit for use with first and second digital computers each having an address bus for supplying addresses and a data bus for supplying data. The access circuit has an address decoder with inputs for the address bus from the first computer, and an address translator circuit having address inputs for addresses supplied by the address bus of the first computer and outputs for translated addresses to the address bus of the second computer. The address translator circuit also has registers selectable by the address decoder and data inputs to program the registers so selected with data from the data bus from the first computer. Also in the access circuit is a port circuit with registers controlled by the address decoder for entry of address information from the data bus of the first computer and assertion of the address information on the address bus of the second computer. Further, a mode control circuit is connected to the address decoder and connected to the data bus to program the mode control circuit to selectively establish operation of the address translator circuit and of the port circuit. Other access circuits, devices, systems and methods are also described.
Abstract:
A memory access system for use with a graphics processor having an address bus, a data bus and a set of control lines. An address translator circuit connected to the address bus of the graphics processor supplies a translated address to a memory upon receipt of an address from the graphics processor. A logic circuit responds to a write signal to automatically increment the translated address and responds to a control signal to return to the translated address. Control circuitry connected to the logic circuit responds to a read signal to supply the control signal to the logic circuit.
Abstract:
A three input arithmetic logic unit (230) forms a mixed arithmetic and Boolean combination of three multibit input signals. The current instruction drives an instruction decoder (250, 245) that generates functions signals F0-F7 which control the combination formed. The three input arithmetic logic unit (230) preferably employs a set of bit circuits (400), each forming carry propagate, generate and kill signals. These signals and a carry input produce a bit resultant and a carry output to the next bit circuit. Selection of the function signals enables the combination to be insensitive to one of the input signals, thus performing a two input function of remaining input signals. The instruction itself may include the function signals and function modification bits, or the function signals and function modification signals may be stored in a special data register. Function modification signals cause modification of the function signals prior to use. The three input arithmetic logic unit (230) includes a least significant bit carry-in generator (246) supplying a carry input to the least significant bit circuit (400). This carry input is determined by the combination being formed, and generally is "1" only during subtraction. The carry input may be specified in the special purpose data register (D0) for certain instructions.
Abstract:
A video random access memory includes memory cells arranged in rows and columns. The columns of memory cells are divided into first and second portions, and the cells of each row of the first portion of memory are interleaved by address with the cells of the same row of the second portion of memory. A first half of a serial register includes a plurality of storage elements that are interleaved by address with a plurality of storage elements of a second half of the serial register. Between the first and second portions of the memory cells, column leads and a multiplexer selectively couple data from either the first portion or the second portion of the columns of the memory cells to either the first half or the second half of the serial register.
Abstract:
The present invention relates to Gray Codes and their conversion to sign and magnitude representation. Gray codes are used in flash ADCs (analogue to digital converters), which convert an analogue waveform into a sampled binary value. This can be done via a thermometer code, and the present invention addresses the issue of the propagation of error due to an indeterminant thermometer code value. In particular the invention provides a Gray code to sign and magnitude converter arranged to produce for the bits of its output other than the sign bit the same code for the Gray codes that are the same distance from the boundary where the sign bit changes value when the Gray codes are arranged in order of their value.
Abstract:
A graphics computer system including a host computer and a graphics processor. The host computer has a host data bus and a host address bus. A first video memory stores color codes corresponding to a display. The first video memory is connected to the host computer permitting it to specify the color codes. A first palette connected to the first video memory has a first look-up table memory for recalling color data words corresponding to color codes received from the first video memory. The first palette is connected to the host computer permitting it to specify the color data words stored in the first look-up table memory. The graphics processor has a local data bus and a local address bus. A second video memory stores color codes corresponding to a display, the graphics processor specifying the color codes stored in the second video memory. A second palette connected to the second video memory has a second look-up table memory. The second palette is connected to the graphics processor permitting it to specify the color data words stored in the second look-up table memory. An interface circuit connects to the host data bus, the host address bus and the second palette. The interface circuit writes data received from the host data bus into the second palette upon detecting predetermined addresses on the host address bus. This causes at least a portion of the second palette to store identical data as stored in corresponding locations of the first palette.
Abstract:
A display buffer includes a plurality of memory banks, each said bank having a plurality of ordered rows of data storage locations. Circuitry controls the storage of a plurality of sequenced lines of display data in said display buffer. A first set of lines of display data is stored at contiguous locations in a first memory bank with the first word of a first line being stored in a location offset from the first location of the first row so a last word of a last line is stored in the last location of the last row. A second set of lines is stored at contiguous locations starting at the first row of the second memory bank. A last line of the second set of lines is stored so that the last word of this last line is stored in the last location of a selected row of the second bank. A third set of lines is stored in a third memory bank starting at a memory line other than the first memory line. If additional space is needed, the display lines wrap around to the first location of the first line of the third bank of memories. A graphics processor may provide the memory addressing and bank selection logic.