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Datasheet Brief 75N42102

Signal Descriptions

Pin Function

I/O

Description

NSE Request Bus:

Request Strobe

Input

This input signifies a valid input request and signals the start of an NSE operation cycle.

Command Bus

Input

Defines the instruction to be performed by the NSE and selects Glo bal Mask registers and Search Result

registers.

Request Data Bus

Input/Output

Three State

The Request Data Bus is a multiplexed address/data bus used to perform reads (and writes) from (to) the

NSE, and to present search data for lookups.

NSE Response Bus:

Index Bus

Output

Three State

This bus is used to drive the address of an ex ternal SRAM, or feedback Lookup result information

directly to the NSE's ASIC/FPGA. The Index Bus contains the encoded location at which the compare

was found.

Chip Enable/ Output Enable

Output

Three State

This signal is driven along with the Index Bus. It is connected to the

CE input pin of a ZBT SRAM or to the

OE pin of a PBSRAM.

Write Enable

Output

Three State

This signal is driven along with the Index bus. It is used to assert the

WE pin of an external SRAM. It is

active for SRAM write operations.

Read Acknowledge

Output

This signal is sent back when the data is read from the NSE on the Request Data Bus, or when the data

being read from the associated external SRAM.

Match Acknowledge

Output

This is signal is sent with the Index. It will be driven low if there was no match, high if a match was found.

Valid

Lookup Bit

Output

This signal is sent with the Index. It will be driven high upon the completion of a lookup, even if the

lookup did not result in a hit.

Clock and Initialization:

Clock Input

Input

All inputs and outputs are referenced to the positive edge of this clock.

Clock Phase Enable

Input

This signal is used to generate an internal clock at ½ the freque ncy of the input clock.

Reset

Input

This pin will force all outputs to a high impedence condition, as well as clearing the NSE enable bit.

Depth Expansion:

Configuration In

Input

Configures the Device ID at power up.

Configuration Out

Output

Configures the Device ID at power up.

Match

Input

Input

The Match Input signal is driven by all upstream Match Output signals. This indicates to all down stream

NSEs that a hit in a higher priority NSE has occurred.

Match

Output

Output

The Match Output signal signifies that a match has occurred in the NSE. The signal is fed into a Match

Input line of all lower priority NSE(s).

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