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IDT79R3052E Datasheet(PDF) 9 Page - Integrated Device Technology |
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IDT79R3052E Datasheet(HTML) 9 Page - Integrated Device Technology |
9 / 23 page 5.3 9 IDT79R3051/79R3052 INTEGRATED RISControllers COMMERCIAL TEMPERATURE RANGE PIN DESCRIPTION PIN NAME I/O DESCRIPTION A/D(31:0) I/O Address/Data: A 32-bit time multiplexed bus which indicates the desired address for a bus transaction in one phase, and which is used to transmit data between the CPU and external memory resources during the rest of the transfer. Bus transactions on this bus are logically separated into two phases: during the first phase, information about the transfer is presented to the memory system to be captured using the ALE output. This information consists of: Address(31:4): The high-order address for the transfer is presented on A/D(31:4). BE BE(3:0): These strobes indicate which bytes of the 32-bit bus will be involved in the transfer, and are represented on A/D(3:0). During write cycles, the bus contains the data to be stored and is driven from the internal write buffer. On read cycles, the bus receives the data from the external resource, in either a single data transaction or in a burst of four words, and places it into the on-chip read buffer. Addr(3:2) O Low Address (3:2) A 2-bit bus which indicates which word is currently expected by the processor. Specifically, this two bit bus presents either the address bits for the single word to be transferred (writes or single datum reads) or functions as a two bit counter starting at ‘00’ for burst read operations. Diag(1) O Diagnostic Pin 1. This output indicates whether the current bus read transaction is due to an on- chip cache miss, and also presents part of the miss address. The value output on this pin is time multiplexed: Cached: During the phase in which the A/D bus presents address information, this pin is an active high output which indicates whether the current read is a result of a cache miss. The value of this pin at this time in other than read cycles is undefined. Miss Address (3): During the remainder of the read operation, this output presents address bit (3) of the address the processor was attempting to reference when the cache miss occurred. Regardless of whether a cache miss is being processed, this pin reports the transfer address during this time. Diag(0) O Diagnostic Pin 0. This output distinguishes cache misses due to instruction references from those due to data references, and presents the remaining bit of the miss address. The value output on this pin is also time multiplexed: I/ D D: If the “Cached” Pin indicates a cache miss, then a high on this pin at this time indicates an instruction reference, and a low indicates a data reference. If the read is not due to a cache miss but rather an uncached reference, then this pin is undefined during this phase. Miss Address (2): During the remainder of the read operation, this output presents address bit (2) of the address the processor was attempting to reference when the cache miss occurred. Regardless of whether a cache miss is being processed, this pin reports the transfer address during this time. ALE O Address Latch Enable: Used to indicate that the A/D bus contains valid address information for the bus transaction. This signal is used by external logic to capture the address for the transfer, typically using transparent latches. DataEn O External Data Enable: This signal indicates that the A/D bus is no longer being driven by the processor during read cycles, and thus the external memory system may enable the drivers of the memory system onto this bus without having a bus conflict occur. During write cycles, or when no bus transaction is occurring, this signal is negated, thus disabling the external memory drivers. 2874 tbl 02 |
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