1-chip microcomputer having controlled access to a memory and IC card using the 1-chip microcomputer

A 1-chip microcomputer, comprising:

• a monitor flag for toggling a flag, indicating that a predetermined address space is being accessed, based on an address bus signal and an instruction read out signal indicative of a first cycle of an instruction;
• an access permission address range setting register operable to set, when said flag is toggled, an address range within which an access is permitted;
• judging means for judging whether or not an access is carried out within the address range thus set during execution of a software;
• an access permission setting register operable to set, when said flag is toggled, a permission for accessing outside the address range;
• and
• control means for controlling an access with respect to a memory based on a result of the judging means and permission set by the access permission setting register,
• wherein the access permission address range setting register and the access permission setting register are readable regardless of whether the flag is toggled or not.

An IC card that uses a 1-chip microcomputer, said 1-chip microcomputer comprising:

• register writing control means for determining whether a writing operation occurs from a predetermined address space or from an address space other than the predetermined address space, and outputting a writing reference signal when the writing operation occurs from the predetermined address space;
• access permission address range setting means for setting an address range within which access by an application program to be executed is permitted only when the writing reference signal is output, such that said access permission address range setting means is operable to set said address range only when a software in a predetermined address space is being executed;
• judging means for judging whether or not an access is carried out within the address range thus set during execution of the application program;
• access permission setting means for setting whether or not an access with respect to an address outside of the address range should be permitted, said access permission setting means being operable to set said access only when the software in the predetermined address space is being executed;
• and
• control means for controlling an access of the application program to a memory based on a result of the judging means and permission set by the access permission setting means.

An IC card that uses a 1-chip microcomputer, said 1-chip microcomputer comprising:

• a monitor flag for toggling a flag, indicating that a predetermined address space is being accessed, based on an address bus signal and an instruction read out signal indicative of a first cycle of an instruction;
• an access permission address range setting register operable to set, when said flag is toggled, an address range within which an access is permitted;
• judging means for judging whether or not an access is carried out within the address range thus set during execution of a software;
• an access permission setting register operable to set, when said flag is toggled, a permission for accessing an address outside the address range;
• and
• control means for controlling an access with respect to a memory based on a result of the judging means and permission set by the access permission setting register,
• wherein the access permission address range setting register and the access permission setting register are readable regardless of whether the flag is toggled or not.