Methods for prioritizing erase and program commands in a nonvolatile semiconductor memory device

A method of prioritizing program and erase commands received in an operation queue for a memory includes the step of storing a placeholder erase command in the operation queue. Subsequent erase commands are absorbed by 1) storing the subsequent erase command in the operation queue; 2) setting a corresponding status indicator for the block designated by the subsequent erase command; and 3) removing the subsequent erase command from the operation queue, wherein the subsequent erase command becomes an absorbed erase command. If a program command that designates a same block as any one of the placeholder and absorbed erase commands is stored in the operation queue, then 1) the same block is erased; 2) the status indicator for the same block is cleared, if the same block is associated with the absorbed command; 3) the program command is executed; and 4) the program command is removed from the operation queue. If the program command does not designate a same block as any one of the placeholder and absorbed erase commands, then 1) the program command is executed; and 2) the program command is removed from the operation queue. In either case, the method then returns to continue absorbing subsequently received erase commands. This allows more erase commands to be queued for execution than what the depth of the operation queue otherwise permits.