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Browse Prior Art Database

Buffer Bubble Data Request Control

IP.com Disclosure Number: IPCOM000060327D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Bentley, SR: AUTHOR [+3]

Abstract

This article describes a data buffer apparatus having the capability of providing a status signal regarding its capability to transfer data between a system and a burst data unit. The data buffer is designed to continuously generate an "allow request" signal if the available storage in the buffer is sufficiently large to accommodate the burst of data to be transferred. The available storage information is like a "bubble" which varies in size and location depending on the amount of data being transferred into or out of the buffer. The "allow request" signal is stopped whenever the bubble size reaches a predetermined threshold value. On reaching the threshold value an overflow latch is set to assure an overflow-free type of operation.

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Buffer Bubble Data Request Control

This article describes a data buffer apparatus having the capability of providing a status signal regarding its capability to transfer data between a system and a burst data unit. The data buffer is designed to continuously generate an "allow request" signal if the available storage in the buffer is sufficiently large to accommodate the burst of data to be transferred. The available storage information is like a "bubble" which varies in size and location depending on the amount of data being transferred into or out of the buffer. The "allow request" signal is stopped whenever the bubble size reaches a predetermined threshold value. On reaching the threshold value an overflow latch is set to assure an overflow-free type of operation. The predetermined value for the bubble size which guarantees an overflow-free type of operation is derived from a mathematical expression as a function of source data rate, destination source data rate, lapsed time between data request and response, and minimum time between requests. The threshold value representing a particular bubble size of various systems and data burst units having different data flow rates can be made programmable to achieve the same control of the "allow request" signal. Fig. 1 shows, in block diagram fashion, the principle of the data request control logic circuit whereby counter 11 receives buffer write signal 15, buffer read signal 16 and reset signal 17. Write signal 15 causes counter 11 to increment the counter, while the read signal 16 will decrement the buffer. Reset signal 17 will reset counter 11 and overflow latch 13 and underflow latch 14. Counter 11 has a borrow output 18 associated with underflow latch 14 at latch input 27 and carry output 19 associated with overflow latch 13 at 26. Fig. 1 also shows NAN...