Abstract: A method and system for transmitting binary-coded data use partitioning of data words in a plurality of data nibbles. The data nibbles are coded using modified a 1-bit hot coding format that transforms a data nibble in a data segment including a plurality of bit groups. A change in a digital state at a bit position in a more significant bit group is maintained at that bit position in less significant bit groups, and information is transmitted in a form of a transition between digital states. The data segments are transmitted in phases each including one bit group from each data segment. At a receiving terminal, the bit groups are converted back in the binary-coded data words. In one application, the invention is used to reduce power consumption during data transmissions to and from an integrated circuit device.

Abstract: A programmable clock generator (220), which is part of an integrated circuit (IC) (210), provides clock signals (230) and (232) to various components of the IC. The clock generator includes a PLL (322) and one or more choppers (326, 328) which provide a desired waveform to the IC for testing purposes. When used in conjunction with a tester (212, 312), the IC can be scan tested at-speed using slower and less expensive testing equipment.

Abstract: Direct memory access controller (DMAC) (54) adapted to directly execute C language style FOR tasks assigned by a processor (70), where the FOR task includes a movement of a data element from a first location to a second location in memory. The DMAC includes multiple execution units (EUs) (88, 90, 92), each to perform an arithmetic or logical operation, and a FOR task controller (80, 82, 86) to perform the data movement. The FOR task controller selects the operation to be performed by the EU. In one embodiment, the FOR task is made up of C language type FOR loops, where descriptors identify the control and body of the loop. The descriptors identify the source of operands for an EU, and the source may be changed within a FOR task. A descriptor specifies a function code for an EU and may specify multiple sets of operands for the EU.

Abstract: Direct memory access controller (DMA) (2) adapted to directly execute C language style FOR tasks, where the FOR task includes a movement of a data element from a first location to a second location in memory, and the movement is controlled by a master DMA engine (MDE) (6). A master DMA engine (MDE) (6) includes a top level state machine (52) to coordinate a context save state machine (54), a parse state machine (56), and a running state machine (58). An loop control descriptor (LCD) queue (74) and a data routing descriptor (DRD) cache store information. The LCD queue allows pipelining of descriptor parsing, while the DRD cache avoids refetching of DRDs on reentry of loops.

Abstract: A data processing system (10) and method is used to recover a CPU from faulty operation. A single timer (38) is used to enable recovery operations. When the timer (38) experiences a first time-out event, a software watchdog interrupt (28) is generated. If the software interrupt (28) is properly handled before another consecutive/subsequent watchdog time out occurs, normal software execution will resume. However, if the software watchdog interrupt is not processed and the watchdog timer (38) experiences a second time-out event while the watchdog time-out interrupt (28) is pending, the timer (38) will generate a bus transfer termination signal (30) and set a status bit (270) within a watchdog status register (44). This assertion of termination signal (30) and the setting of the bit (270) allows the microprocessor to determine that a locked bus state exists.

Abstract: A synchronous memory interface feeds back a buffered (34) clock signal to a microcontroller (20) to simplify and improve output hold time for the memory (38). An output delay circuit (36) in the microcontroller (20) is controlled by the same delayed clock signal as the synchronous memory (38). This delay circuit (36) selectively delays memory signals to the synchronous memory (38) from the microcontroller delay circuit (36). The use of flip-flops (40, 44) in the delay circuit (36) provides a mechanism for scan testing. This enables three different selectable modes of operation of the delay circuit (36) providing flexibility in interfacing in different environments.

Abstract: When a processor (102) issues a request for an address (502), a determination is made as to whether or not the address is contained within a buffer (103) or cache associated with the processor (102), or the address is contained within a line of data currently being fetched from an external memory system (105). If the address is not contained within the buffer or cache and is not contained within a line being currently fetched, the current fetch will be cancelled (515, 516).

Abstract: A bus interface unit within a processor ensures a delay period after the occurrence of a read operation to avoid bus contention on a multiplexed bus, When there is a requirement for a back-to-back read or write operation subsequent to the read bus cycle on a multiplexed bus it is important to allow devices, such as memory, sufficient time to reset after transmission of data. To avoid the bus contention problem that occurs after a read bus cycle, i.e, prevent a next address on the bus until the bus is in a tri-state condition, one embodiment inserts idle clock cycles subsequent to a read but not subsequent to a write, The present invention avoids bus contention on a multiplexed bus while providing flexibility in interfacing with a variety of memory devices, and providing a flexible processor design.

Abstract: Circuitry is implemented within an integrated circuit ("chip") (101) which is an IEEE 1149.1 compliant device capable of performing JTAG testing (104), such as an EXTEST or CLAMP testing procedure. Upon exiting of either of these procedures, the input/output pins (210) of the chip are placed in a known state, which may be a high impedance state.

Abstract: A data processing system (10) having a bus controller (5) that uses a communication bus (22) which adapts to various system resources (7) and is capable of burst transfers. In one embodiment, the processor core (2) and system resources (7) supply control signals supplying required parameters of the next transfer. The bus controller is capable of transferring operands and/or instructions in incremental bursts from these system resources. Each transfer data burst has an associated unique access address where successive bytes of data are associated with sequential addresses and the burst increment equals the data port size. The burst capability is dependent on the ability of system resource (7) to burst data and can be inhibited with a transfer burst inhibit signal. The length of the desired data is controlled by a sizing signal from the core (2) or from cache and the increment size is supplied by the resource (7).

Abstract: A data processing system (10) having a bus controller (5) and a multiplexed communication bus (22) and provides a portion of the valid address information during the data phase. In one embodiment, in response to an address extension control signal, the bus controller (5) allocates the communication bus (22) to provide the address extension on conductors not needed for data, reducing the need for address latch circuitry. In an alternate embodiment, the bus controller (5) provides burst transfers where the processor core (2) increments a portion of each address with each data in the burst. For such burst transfers, the length of the desired data is controlled by a sizing signal (42) from the core (2) or from cache and the increment size is supplied by the system resource (7).

Abstract: A method and apparatus for providing both power and control by way of an integrated circuit terminal (22). In one form, a clock source (12) supplies a periodic signal to a phase lock loop circuit (32) and to a multiplexer (34). The output of the phase lock loop circuit (32) is a second input to the multiplexer (34). The phase lock loop circuit (32) receives its power from a power and control pin (22). The multiplexer (34) receives its power from a power pin (24). The power and control pin (22) is used as a control input to multiplexer (34). Multiplexer (34) uses the power and control pin (22) to select which input to output as a system clock.

Abstract: A data processor has an input synchronizer (10) which is dynamically enabled by a plurality of control signals provided by a user of the data processor. When the plurality of control signals has a predetermined logic level, a bias generator enable circuit (18) enables a bias generator (16). Subsequently, bias generator (16) enables a differential amplifier (12) to synchronize an asynchronous input signal to an operating frequency of the data processor. When the plurality of control signals does not have the predetermined logic level, bias generator enable circuit (18) disables bias generator (16). Subsequently, differential amplifier (12) is disabled and the asynchronous input is not synchronized with the internal operating frequency of the data processor. Therefore, because the user may choose the logic levels of each of the plurality of control signals, the user may dynamically disable input synchronizer (10) to minimize the power consumption of the data processor.

Abstract: A method and apparatus for reducing power consumption in a data processing system by interrupting the supply of clocking pulses to selected portions of the system in response to a power-down signal provided by a data processing portion of the system only if the state of a respective control signal indicates that that particular portion of the system is then disabled or otherwise inhibited from interrupting the operation of the data processing portion.

Abstract: A system for interfacing a Processor to a Coprocessor using standard bus cycles. The Processor, upon encountering in its instruction stream an instruction having a particular Operation word format, will transfer a Command word following the Operation word to a particular Coprocessor designated by a Coprocessor Identity field in the Operation word. Upon decoding the Command word, the Coprocessor will respond with any of a set of response primitives which define functions which the Coprocessor requires to Processor to perform in support of the Command by the Coprocessor. The interface provides for all functions which the Coprocessor may require, including selective vectoring to appropriate exception handlers.

Abstract: In a data processing system having a first bus sized to accomodate 2.sup.x units of data and a second bus sized to accomodate 2.sup.y units of data, where x and y are positive integers and y is less than or equal to x, a method and apparatus for determining y from the x least significant bits of a control address, concatenated with a decode control bit, and then decoding the (x-y) most significant bits of the x control address bits to determine which of x data unit transceivers coupled between the first and second buses should be enabled.

Abstract: A mode selection circuit is disclosed which is suitable for configuring a data processor at the time at which the data processor is initialized with a reset signal. Mode selection latches are coupled to terminals normally used as an input/output port for the data processor and the latches are clocked with a signal generated by a level detector circuit which senses the reset signal. The mode selection latches are programmed by applying appropriate logic levels to the terminals of the input/output port at the time at which the data processor is being reset. The circuitry is adapted for allowing the connection of a diode from a terminal of the input/output port to the reset terminal of the data processor in order to program a low logic level into the corresponding mode detection latch.