Microprogramavel system architecture of word of memory to control distributed

摘要

A method and apparatus for a microinstruction controlled unit having multiple subunits which are controlled by microoperations encoded within microinstructions from a control store. One master subunit controls the order in which the microinstructions are executed by generating the address of the next microinstruction to be read from the control store. The method provides for the overlapping of the execution of a current microinstruction while the next microinstruction is being addressed and read from the control store. The control store is divided into control substores with each control substore located near the subunit which executes the microoperations stored in its associated control substore. Subunits can affect the order of microinstruction execution by causing a trap in the master subunit which will cause the next microinstruction to be read from a predefined address within the control store. If required, the master subunit can read in status information from the subunits in order to determine the condition within the subunits that caused the trap to occur. A means is provided for storing a return address which allows for rexecution to continue at the next microinstruction that would have executed had a trap not occurred.