Abstract: A processor-based system such as a workstation or server, using a system clock provided through a phase-locked loop (PLL) to a clock gate and then to a clock tree, which distributes the core system clock to components in the processor-based system, including a host bridge circuit. The host bridge distributes control signals to a receiving device such as a memory module, which may use a continued clocking signal when the system enters a low-power mode. A feedback clock for the PLL is provided to the receiving devices during low-power mode to ensure continued clocking, when the clock gate output is low and the clock tree is thereby disabled. A skew compensation circuit coordinates clocking in the continued clock and the core system clock.

Abstract: A circuit and method for stopping a clock tree while maintaining PLL lock. A clock circuit includes a locked loop circuit and a clock tree distribution network. The locked loop circuit receives an input clock signal and generates a PLL output clock depending upon a feedback signal. The clock tree is coupled to the locked loop circuit and conveys the PLL output clock to a plurality of clocked circuit elements. The clock circuit further includes a gating circuit and a feedback delay circuit. The gating circuit is coupled between the locked loop circuit the clock tree distribution network and selectively inhibits the PLL output clock from clocking the clock tree distribution network. The feedback delay circuit provides the feedback signal, which represents a delayed version of the PLL output clock, during operation including when the gating circuit inhibits the PLL output clock from clocking the clock tree.

Abstract: A flexible address mapping method and mechanism allows mapping regions of a microcontroller's memory and I/O address spaces for a variety of applications by defining memory regions which are mapped to one of a set of physical devices by a programmable address mapper controlled by a set of programmable address registers. The mapping allows setting attributes for a memory region to prohibit writes, caching, and code execution. A deterministic priority scheme allows memory regions to overlap, mapping addresses in overlapping regions to the device specified by the highest priority programmable address register.

Abstract: A processor-based system provides communication among multiple computer devices operating at different frequencies utilizing clock synchronization. Phase relationship is maintained between clock signals running a different frequencies such that a read cycle of a device operated at the faster frequency is initiated when the clock signals are in phase. A write cycle of the faster frequency device is initiated when the clock signals are out of phase. A synchronization signal is generated by sampling the clock signals together to indicate the phase relationship. In addition, a return clock, derived from the faster clock, drives external devices. Information sent from internal devices to external devices are passed through a register driven by the return clock. Timing delays for information presented to the external devices is avoided as the register transmits all information according to the return clock. Return data is clocked into a return register also according to the return clock.

Abstract: A processor-oriented system, such as a microcontroller or computer system, supports a programmable address decoder used to redirect accesses to unassigned I/O address space. I/O accesses to unassigned addresses or address holes can be directed to multiple busses. If a programmable switch associated with the programmable address decoder is set to a first predetermined value, then certain I/O addresses are directed to a first bus. If the programmable switch associated with the programmable address decoder is set to a second predetermined value, then certain I/O addresses are directed to a second bus. If the first bus is coupled to PC/AT compatible peripheral devices and the second bus is coupled to non-PC/AT compatible devices, then the I/O address redirection capability selectively supports a PC/AT compatible mode or a non-PC/AT compatible mode. Certain integrated devices coupled to the second bus can be bypassed or disabled as desired to allow redirection of I/O to external devices coupled to the first bus.

Abstract: A direct memory access (DMA) controller provides seven DMA channels configurable for a PC/AT compatible mode or an enhanced mode. In an enhanced mode of the DMA controller, three DMA master channels on a master DMA controller and a DMA channel on a slave DMA controller are individually configurable to be either 8-bit or 16-bit DMA channels. In addition, in the enhanced mode, a memory address can increment or decrement across a memory page boundary. The DMA controller includes a transfer count register selectively configured for 16-bit operation or 24-bit operation. The DMA controller also includes address generation logic selectively configured for 24-bit operation or 28-bit operation. In the PC/AT compatible mode, the DMA controller supports three 16-bit channels and four 8-bit channels. The DMA controller thus provides DMA channel width configurability.

Abstract: A flexible address mapping method and mechanism allows mapping regions of a microcontroller's memory and I/O address spaces for a variety of applications by defining memory regions which are mapped to one of a set of physical devices by a programmable address mapper controlled by a set of programmable address registers. The mapping allows setting attributes for a memory region to prohibit writes, caching, and code execution. A deterministic priority scheme allows memory regions to overlap, mapping addresses in overlapping regions to the device specified by the highest priority programmable address register.

Abstract: A circuit for dynamic signal drive strength compensation. A circuit for compensating the drive strength of an output signal includes an output driver stage including a driver circuit and a drive strength control circuit. The driver circuit may be selectively enabled depending upon a drive strength indicator signal. The driver circuit includes a P-channel transistor which has a P input which is controlled by a P-channel control signal. The driver circuit also includes an N-channel transistor which has an N input which is controlled by an N-channel control signal. The drive strength control circuit may generate the respective P-channel and N-channel control signals. The P-channel control signal is prevented from changing while the P-channel transistor is turned on. The N-channel control signal is prevented from changing while the N-channel transistor is turned on.

Abstract: A microcontroller provides a flexible architecture to readily support both general embedded applications and communications applications. The microcontroller includes an embedded processor, a relatively low-speed general purpose peripheral bus controller, a relatively high-speed peripheral bus host bridge, a primary memory controller, and a secondary memory controller, each coupled to a processor bus. The general purpose peripheral bus controller is coupled to a relatively low-speed general purpose peripheral bus which is coupled to a plurality of integrated general purpose peripherals. The relatively high-speed peripheral bus host bridge is coupled to a relatively high-speed peripheral bus capable of supporting a plurality of communication-oriented peripherals. The secondary memory controller shares an address bus with the general purpose peripheral bus controller and shares a data bus with either the primary memory controller or the general purpose peripheral bus controller.

Abstract: A microcontroller for PC/AT-compatible or non-PC/AT compatible embedded environments is disclosed. The microcontroller includes a general purpose bus which may emulate an ISA bus in a PC/AT-compatible mode. PC/AT-compatible DMA channels, interrupt controllers, programmable timers, a real-time clock, processor, and a flexible memory and an I/O mapping scheme are provided by the microcontroller. The programmable timers, interrupt controllers, DMA channels and I/O mapping can be configured for a PC/AT-compatible mode or a non-PC/AT-compatible mode. In particular, the plurality of interrupt controllers are configured such that some are enabled during PC/AT-compatible operation while the remainder are disabled. The microcontroller further embeds several PC/AT peripheral devices and yet maintains the flexibility to support external devices if desired by the embedded system designer. Other PC/AT-compatible features are also supported by the microcontroller.

Abstract: A programmable interrupt controller arrangement is provided including a multiple number of selectably enabled programmable interrupt controllers along with a multi-channel switch matrix. A scalable number of interrupt sources can be routed to any particular interrupt request line. In addition, from the same architecture, multiple interrupt sources are allowed to share any one of the interrupt request lines. Interrupt signals are routed via the switch matrix under software control. PC/AT compatibility is achieved by selectively disabling certain of the programmable interrupt controllers.

Abstract: A computer system is provided including a CPU, a graphics controller, system memory, data steering logic, a DMA controller and arbitration logic. The graphics controller and system memory are coupled to a high-speed data bus. Data accessed by the CPU, the DMA controller and the graphics controller is all stored in the system memory. The data steering logic is also coupled to the high-speed data bus and to a low-speed data bus, and to the CPU. The data steering logic is configured to selectively couple the CPU to either the high-speed data bus or the low-speed data bus, thereby accommodating data transfers between the CPU and a bus device connected to the slow-speed data bus concurrent with data transfers between the graphics controller and the system memory. The data steering logic may also accommodate data transfers by the DMA controller on the slow-speed data bus concurrent with graphics controller data transfers.

Abstract: An integrated processor is fabricated on a single monolithic circuit and employs circuitry to accommodate data-intensive, view-intensive and voice-intensive requirements of modern-day PIDs. The integrated processor includes a CPU core, a memory controller, and a variety of peripheral devices to achieve versatility and high performance functionality. The integrated processor consumes less power by provision of a clock control unit including a plurality of phase-locked loops for generating clock signals of differing frequencies to appropriately clock the various subsystems of the integrated processor. The clock signals provided to the various subsystems by the clock control unit are derived from a single crystal oscillator input signal. A power management unit is incorporated within the integrated processor to control the frequency and/or application of certain clock signals to the various subsystems, as well as to control other power management related functions.

Abstract: Within an integrated circuit, an input/output driver circuit is provided. The input/output driver circuit is configured to provide electrical isolation and power savings when the integrated circuit is configured into a computer system such as a personal information device. By providing a mechanism permitting removal of power from the driver circuit, the integrated circuit inhibits current flow from the integrated circuit into a powered-down peripheral device. A force term is activated, when electrical isolation is desired, to inhibit current flow into or from the integrated circuit via an input/output pad voltage level. A power savings is enabled by allowing the power down of peripheral devices coupled to the integrated circuit without the need for external buffer circuits.

Abstract: The disclosed portable back carrier is formed of flexible generally nonextendable strap means, to have shoulder loops, link straps connected off of the shoulder loops, and foot loops connected off of the link straps. A strap is connected between the shoulder loops, to locate the loops on the carrying person and to fit around the carried person's upper body. A strap is connected off of the load links, just above the foot loops, to locate the loops on the carrying person and to fit around the carrying person's midsection. Release buckles and friction slides may be incorporated in the straps to allow the back carrier to be easily used by both the carrying person and the carried person, and to fit such persons of different sizes.