Method and circuitry for queuing snooping, prioritizing and suspending

Abstract

A method of, and apparatus for, storing and prioritizing among erase block and program word commands is described for a nonvolatile memory device. This prevents the depth of an operation queue responsible for queuing program and erase commands from limiting the number of erase commands that are stored at one time. The first erase command received serves as a place holder, holding a place within the operation queue for all subsequently received erase commands. All subsequently received erase commands are absorbed and cleared from the operation queue. As a result, the operation queue may receive additional commands and an erase command may be queued for every block of memory within the nonvolatile memory device. Absorbed erase commands can be prioritized in response to subsequently received program commands. Blocks are flagged for priority erasure using a priority register. Additionally, interrupt windows located at safe points permit interruption of erase operations to handle command interrupts. The erasure of one or more blocks can be suspended so that a program word command can be serviced thereby permitting program word commands to jump ahead of erase block commands in the queue. Furthermore, a query can be made to determine the status of any block and the block status query will consider pending commands in the operation queue when determining the block status for the block queried.