Browse Prior Art Database

Read and Store LIFO Stack Pointers

IP.com Disclosure Number: IPCOM000087334D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Stoops, EH: AUTHOR

Abstract

Counters 1 and 2 act as address pointers for the last-in-first-out (LIFO) memory or stack 3. Store pointer 1 points to the first empty location, and read pointer 2 points to the last full location.

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Read and Store LIFO Stack Pointers

Counters 1 and 2 act as address pointers for the last-in-first-out (LIFO) memory or stack 3. Store pointer 1 points to the first empty location, and read pointer 2 points to the last full location.

Initially, both counters 1 and 2 are reset by the INITIAL RESET signal to zero counts and are pointing via gates 4-6 to the first memory location (i.e., the 0 address location), which is empty and awaiting the entry of DATA IN. In response to the enable signal STORE, the first operation is a store and the DATA IN information is stored in the first location. At the end of the first store operation, store counter 1 is incremented to the one count by a command signal STORE INCREMENT. The latter is decoded by appropriate logic (not shown) which detects that both counters 1 and 2 contain zero before the particular increment is made.

Pointers or counters 1 and 2 are now in their normal states. Read pointer 2 is still pointing to the last full location (i.e., the 0 address location), whereas store pointer 1 is now pointing to the first empty location (i.e., the 1 address location). By appropriate logic (not shown) both counters 1 and 2 are incremented to their respective next higher counts following the next store operation, i.e., to counts 2 and 1, respectively. Similarly, subsequent read operations decrement both counters 1 and 2 to their next lowest count, except in the case where the read pointer 2 is already at the zero count, in which...