Abstract: Systems and methods for transferring control between programs of different security levels are described herein. Some embodiments include a processor capable of operating at one or more security levels including a first and a second security level, a memory system coupled to the processor (the memory system stores a first program that executes on the processor at the first security level, and a second program that executes on the processor at the second security level), and a register configured to store an entry point address to the first program (wherein an instruction that executes on the processor at the second security level is blocked from writing values to the register). A transfer of control from the second program to the first program is executed if the register provides the entry point address. The transfer of control is blocked if the entry point address is not provided by the register.

Abstract: Disclosed herein is a system and method of operating a processor before and after a reset has been asserted. Prior to a reset being asserted the processor operates in one of a plurality of states wherein primary code may be executed by the processor depending on said state. Upon a reset being asserted the processor begins executing code for a reset routine. The processor also executes a process such that the processor operates in the same state it was in prior to the reset upon the reset no longer being asserted.

Abstract: A data processing system on an integrated circuit 42 with microprocessor 1 and peripheral devices 60-61 is provided with an emulation unit 50 which allows debugging and emulation of integrated circuit 42 when connected to an external test system 51. Microprocessor 1 has in instruction execution pipeline which has several execution phases which involve fetch/decode units 10a-c and functional execution units 12, 14, 16 and 18. The pipeline of microprocessor 1 is unprotected so that memory access latency to data memory 22 and register file 20 can be utilized by system program code which is stored in instruction memory 23. Emulation unit 50 provides means for emulating the unprotected pipeline of microprocessor 1 and for rapidly uploading and downloading memories 22-23. Emulation unit 50 operates in a manner to prevent extraneous operations from occurring which could otherwise affect memories 22-23 or peripheral devices 60-61 during emulation.

Abstract: A data processing system on an integrated circuit 42 with microprocessor 1 and peripheral devices 60-61 is provided with an emulation unit 50 which allows debugging and emulation of integrated circuit 42 when connected to an external test system 51. Microprocessor 1 has in instruction execution pipeline which has several execution phases which involve fetch/decode units 10a-c and functional execution units 12, 14, 16 and 18. The pipeline of microprocessor 1 is unprotected so that memory access latency to data memory 22 and register file 20 can be utilized by system program code which is stored in instruction memory 23. Emulation unit 50 provides means for emulating the unprotected pipeline of microprocessor 1 and for rapidly uploading and downloading memories 22-23. Emulation unit 50 operates in a manner to prevent extraneous operations from occurring which could otherwise affect memories 22-23 or peripheral devices 60-61 during emulation.