Arrangements having security protection

A bus interface method useable in an apparatus having an internal bus and connected to an external bus, the method comprising:

• receiving, via an access control unit, an access request sent through the external bus, and
• determining, via an access judging unit connected to the access control unit, whether the access request sent through the external bus is to be honored or rejected,
• wherein the access control unit, upon receiving the access request sent through the external bus, sends to the access judging unit an access judging check request signal asking whether the requested address falls within one of the access-permitted areas registered in the access judging unit,
• the access judging unit checks whether the requested address falls within one of the access-permitted areas registered in it and returns to the access control unit, an access judging check result signal indicating whether the access request is to be honored or rejected, and
• and if the access judging check result signal indicates that the access request is to be rejected, the access control unit nullifies the access request.

An external bus interface method useable within an apparatus including a processor core for performing computation, an external bus interface unit for connecting to an external bus, a memory interface unit for controlling access to a local memory, and an internal bus that interconnects the processor core, the external bus interface unit, and the memory interface unit, the method comprising:

• receiving, via an access control unit, an write request conveyed through the external bus, and
• judging, via an access judging unit connected to the access control unit, whether the write request is to be honored or rejected,
• wherein upon receiving the write request conveyed through the external bus, the access control unit sends to the access judging unit an access judging check request signal asking whether the requested address falls within one of the access-permitted areas registered in the access judging unit,
• the access judging unit checks whether the requested address falls within one of the access-permitted areas registered in it and returns to the access control unit, an access judging check result signal indicating whether the write request is to be honored or rejected,
• and if the access judging check result signal indicates that the write request is to be rejected, the access control unit nullifies the write request.