Abstract: The present invention provides a speculatively loaded memory for use in a data processing system. The present invention may include a memory block including rows each identified by an address. A first register may store a first address of the memory block and a second register may store a second address of the memory block. A control circuit may be coupled to the first and second registers, and may receive control signals. The control circuit causes contents of the first register to be stored into the second register in response to a first state of the control signals, and the control circuit causes contents of the second register to be stored into the first register in response to a second state of the control signals.

Abstract: A memory system includes a memory array for storing a plurality of data elements, the memory array comprising a plurality of memory blocks. In one embodiment, the data element are tag string data. The memory system may also include a comparator unit coupled to receive a memory block output and an input signal, wherein when the memory block output matches the input signal, the memory system transmits a match signal and a code word on a result bus. In one embodiment, data elements are stored as fragments in different portions of the memory array. The input signal may be received as fragments and compared to the data elements over different time periods. In one embodiment, the present invention provides a memory lookup system and method that supports multiple protocols.

Abstract: Accordingly, the present invention provides a method for synchronously accessing memory in order to improve the performance in systems which use memories with slower cores. A first address for a first memory access is provided during a first clock period. A first control signal to indicate an address phase of the first memory access is activated during the first clock period. A second control signal to indicate a data phase of the first memory access is activated during a second clock period subsequent to the first clock period. A first data element accessed by the first address is received during a third clock period immediately subsequent to the second clock period. A second address for a second memory access is provided during the third clock period. The first control signal indicating an address phase of the second memory access is activated during the third clock period.

Abstract: A method and apparatus for providing an external indication of internal cycles in a data processing system (10) in order to more easily debug software being executed by data processing system (10). In one embodiment, data processing system (10) provides cycle type signals (14) external to data processing system (10). The cycle type signals (14) can be used to determine a variety of information about the activity and bus cycles being performed within data processing system (10), activity which is not readily discernible except by way of the cycle type signals (14). In some cases the information provided by the cycle type signals (14) is sufficient for debug purposes; in other cases, information from additional signals, e.g. the address type signals (15) and the read/write signal (19) may also be required.

Abstract: An integrated circuit microprocessor (30) accesses external memory using internally-generated control signals having programmable memory access interface types. A register (61), associated with a memory region, stores an encoded value. During an access to that memory region, a decoder (63) decodes the encoded value to provide a decoded signal. If the decoded signal is in a legal state, then an access controller (64) activates external control signals with timing corresponding to the legal state. If the decoded signal is in a reserved state, then the access controller (64) prevents the access from taking place by keeping the external control signals inactive, preventing software errors from resulting in illegal accesses.

Abstract: Method and apparatus in a data processing system (10) for selectively inserting bus cycle idle time. The present invention allows a data processing system (10) to selectively insert a predetermined number of idle clocks at the end of a bus cycle. In one embodiment of the present invention, there is a base register (48) and an option register (46) corresponding to each one of the chip select terminals (73). In one embodiment of the present invention, each option register (46) includes a user programmable idle control bit (110). If a first chip select is used to select a peripheral device during a bus cycle to that same peripheral device, the idle control bit (110) which corresponds to the first chip select determines whether or not one or more idle clocks will be inserted after that bus cycle.

Abstract: A data processor (30) includes a multi-level protection circuit (50) which enables the generation of external control signals. The multi-level protection circuit (50) defines regions of protection (41, 42), which may be nested. The protection circuit (50) checks access cycle attributes such as read or write, supervisor or user, and data or instruction. First (51) and second (54) decoders are associated with each other and define two regions (41, 42) which may overlap. When a CPU (31) accesses a memory location within both regions, the protection attributes of the second decoder (54), at a higher priority level than the first decoder (51), control. If an attempted access violates the programmable protection attributes of the second region (42), then the multi-level protection circuit (50) prevents the access from occurring, even though the access attributes of the first decoder (51) alone would enable the access.

Abstract: A modular chip select control circuit (80) is scalable by having an address decode stage (90) with a first number of address decoders, a control stage (100) with a second number of control units, and a pin configuration stage (110) with a third number of pin configuration logic circuits. These three numbers, defining the number of memory regions, the access pipeline depth, and the number of chip select signals, respectively, are independent and may be changed between chip designs to accommodate different system needs. The control stage includes an early pipeline control circuit (186) which allows the control units (170, 180) to pipeline pending memory cycles, based on an accessed region's characteristics. The early pipeline control circuit (186) together with the control units (170, 180) enforce a set of pipelining rules to ensure data integrity and proper cycle termination, thus providing an efficient series of pipelined memory access cycles.

Abstract: A pin configuration logic circuit (120) has a pin function register (130) which defines a selected pin function, such as chip enable, write enable, and output enable, to be provided as a chip select signal. The logic circuit (120) allows an arbitrary pipeline length by causing the chip select signal to obey only the timing of the active cycle. For a two-deep access pipeline, the logic circuit (120) marks whether a first or a second cycle owns the pin. The pin configuration logic circuit (120) uses the timing associated with the selected pin function to provide the chip select signal during the first cycle if the attributes of the cycle, such as an access to a region programmed in the pin function register, are met. During the second cycle, the pin configuration logic circuit (120) further obeys the timing associated with the selected pin function if the attributes of that cycle are also met.

Abstract: An integrated circuit microprocessor (30) reads data from an external memory device (22, 23) through early overlapping memory access cycles, thus allowing efficient accesses to slower-speed memory. The microprocessor (30) drives a first address and activates a chip enable signal during a first clock period. The chip enable signal causes the external memory device to latch the first address and begin a first memory access. During a second, subsequent clock period, the microprocessor (30) provides a second address and again activates the chip enable signal. During a third clock period, subsequent to the second clock period, the microprocessor (30) latches a first data element associated with the first address. This early overlapping memory access type allows a memory device with a slow memory core to pipeline the second access prior to completion of the first access, increasing system efficiency.