摘要:
A non-volatile memory controller is provided which is connectable directly to the local bus of a computer system and which allows access to one or more 32-bit banks of ROM and to an 8-bit bank of non-volatile memory. The 8-bit bank of non-volatile memory may be used, for example, to store BIOS code, and may be implemented using a ROM or flash memory device. The non-volatile memory controller includes a data router, a sequencer, and a set of output latches for routing the 8-bit BIOS code (stored within the 8-bit bank) to selected byte lanes of the local bus and for converting the 8-bit data to 32-bit local bus data. The non-volatile memory controller further supports high performance, 32-bit accesses to the user software stored within the 32-bit banks. If the system designer or user instead must maximize the memory capacity of the computer system, the 8-bit bank of memory may be replaced with a larger 32-bit bank of memory. In this configuration, a control signal is provided to the non-volatile memory controller to indicate that a 32-bit bank is connected rather than an 8-bit bank. The control signal causes the sequencer and the data router to be disabled. When a memory access to the 32-bit bank is executed, the non-volatile memory controller accesses the data within the 32-bit bank and drives the data directly on the CPU local bus.
摘要:
An integrated processor that employs a bus interface unit to accommodate high performance data transfers via an external peripheral interconnect bus with multiplexed address/data lines. The peripheral interconnect bus, which may be a PCI standard bus, accommodates data transfers between an internal bus of the integrated processor and PCI peripheral devices. The integrated processor further includes a sub-bus control unit that generates a set of side-band control signals that allow the external derivation of a lower performance secondary bus, such as an ISA bus, without requiring a complete set of external pins for the secondary bus on the integrated processor. The derivation of the secondary bus is accomplished with an external data buffer and an external address latch which are controlled by the side-band control signals. Separate address and data lines from the integrated processor for the secondary bus are not required. Accordingly, high performance peripheral devices are supported by the integrated processor as well as lower performance, lower-cost peripherals without a significant increase in the pin-count of the integrated processor. Accordingly, overall cost of the integrated processor is kept low while a wide range of peripheral devices are supported.
摘要:
A non-volatile memory chip enable encoding method allows the storage of both boot code and user application software within a common memory array. The chip enable encoding method further allows a variable number of memory banks to be provided within the non-volatile memory array and allows the system to power-up and execute the boot code before the array configurations are selected by firmware. In one embodiment, a memory controller includes four chip enable output lines for selectively enabling a plurality of ROM banks. One of the ROM banks includes boot code that is executed by the system microprocessor during system boot. If the user requires a ROM array consisting of four ROM banks, a separate chip enable output line is connected to each ROM bank. If the user instead requires a ROM array consisting of, for example, eight ROM banks, an external decoder may be connected to the four chip enable output lines. In this configuration, each output line of the decoder is coupled to a respective bank enable input line of the ROM banks. In either configuration, the chip enable lines are driven in a mutually exclusive relationship during system boot to access the boot code (stored within one of the ROM banks). Subsequently, the encoding of the chip enable signals at the chip enable output lines of the memory controller is dependent upon configuration information stored in a configuration register.
摘要:
An apparatus for use with a host computing system for controlling access to a first data bus which is external of the host computing system and which first data bus is operatively connected with a second data bus internal of the host computing system. The apparatus comprises a local processing unit which is configured substantially the same as the host processing unit and is driven by a separate local program distinct from the host processing program driving the host processing unit. The apparatus further comprises a supplemental processing circuit for processing information, which supplemental processing circuit is responsive to the host processing unit and to the local processing unit to determine whether the host processing unit or the local processing unit has operative access to the first data bus. In its preferred embodiment, the first data bus and the second data bus are operatively connected by a configurable buffer circuit for effecting data bus connection. Further, in the preferred embodiment of the present invention, the supplemental processing circuit generates an intervention signal in response to the local processing unit, the buffer circuit responding to the intervention signal by configuring appropriately to provide operative access by the apparatus of the second data bus.
摘要:
A direct memory access controller is provided that performs DMA transfers by executing both a memory access cycle and an I/O access cycle. During the memory access cycle, the address location of system memory to be accessed is driven on the addressing lines of a local bus. During the I/O access cycle, an address value within a DMA configuration address range is driven on the address lines of the local bus. The DMA configuration address range is the range of address values to which the configuration registers of the DMA controller are mapped for receiving initialization data. Accordingly, other peripheral devices that may be connected to the local bus will not respond to the I/O access cycle. An address disable signal is further not required to disable the address decoders of other I/O peripheral devices not involved in the DMA transfer. Since the memory access cycle and the I/O access cycle of the DMA transfer are identical to those executed by the system microprocessor, subsystems are not required to respond to specialized DMA protocols. Finally, although the DMA controller implements two-cycle DMA transfers, the DMA controller is compatible with conventional peripheral devices which assume one-cycle DMA transfer protocols.
摘要:
A direct memory access controller implements a two-cycle approach for performing a desired DMA transfer by executing both a memory access cycle and an I/O access cycle. During the memory access cycle, the address location of system memory to be accessed is driven on the addressing lines of a local bus. During the I/O access cycle, an address value within a DMA configuration address range is driven on the address lines of the local bus. The lower two order bits of the address value are encoded to provide byte lane information to a peripheral device during the I.backslash.O access cycle. The peripheral device responsively receives or provides data at the specified byte lane. As a result, peripheral devices that may be connected to the local bus will not respond to the I/O access cycle, while encoded byte lane information is provided to the desired peripheral device without requiring dedicated byte select lines.
摘要:
An integrated processor is provided that includes a CPU core coupled to a variety of on-chip peripheral devices such as a DMA controller, an interrupt controller, and a timer. The integrated processor further includes a power management message unit coupled to the DMA controller, interrupt controller, and timer for monitoring the internal interrupt and bus request signals of the integrated processor. The power management message unit may also monitor other selected activities of the integrated processor such as activities of a floating-point coprocessing subunit. Based on the detected activities, if any, the power management message unit encodes a message on a power management message bus to thereby provide information regarding the internal events of the integrated processor to an external power management unit. Power management decisions are made by an external power management unit. The power management unit receives the encoded messages on the power management message bus and responsively makes decisions as to the appropriate power management mode to enter. The power management unit includes a clock control unit coupled to an internal clock generator of the integrated processor for controlling the frequencies of a CPU clock signal and a system clock signal. The power management unit further includes a power control unit for controlling the application of power to various external peripheral devices.
摘要:
A programmable interrupt controller is provided for use in computer systems including one or more CPUs. The programmable interrupt controller includes an interrupt request interface, a storage device, and at least one processor interface having an interrupt nesting buffer. An interrupt request identification code is assigned to each interrupt request and stored in the nesting buffer. The interrupt request identification codes used to reference the interrupt requests are stored in order of their priority. Each nesting buffer need have only a number of entries equal to the number of priority levels.
摘要:
An interrupt controller includes an interrupt request register for receiving interrupt requests from various peripherals or I/O devices via a set of request lines. A priority resolver is further provided for comparing the priority level of the interrupt lines, latching the lower priority requests in a stand-by mode, and directing servicing of the highest priority level. An in-service register is provided for storing the identification of any request line that is being serviced by the microprocessor. In one embodiment, a set of signal lines are coupled between the in-service register and external terminals of the integrated circuit on which the interrupt controller is fabricated. A power management unit may be coupled to the external pins of the integrated circuit and thereby receives real-time information regarding an interrupt request that is currently being serviced and regarding interrupt service routines that have completed. Using this information, the power management unit advantageously stops unused clock signals and/or removes power from inactive circuit portions when an interrupt routine completes without having to estimate the time of completion. By accurately stopping unused clock signals and removing power, a reduction in the overall power consumption of the computer system can be attained.
摘要:
An integrated processor is provided that includes a CPU core coupled to a variety of on-chip peripheral devices such as a DMA controller, an interrupt controller, and a timer. The integrated processor further includes a power management message unit coupled to the DMA controller, interrupt controller, and timer for monitoring the internal interrupt and bus request signals of the integrated processor. The power management message unit may also monitor other selected activities of the integrated processor depending upon the system requirements. Based on the detected activities, if any, the power management message unit encodes a message on a power management message bus to thereby provide information regarding the internal events of the integrated processor to an outside power management unit. The power management message bus is channeled from the integrated processor at a set of package pins that are isolated from the standard external peripheral bus of the integrated processor. By providing encoded information regarding the internal events of the integrated processor, monitoring of such events by an external power management unit is possible while the number of external pins on the integrated processor are minimized.