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Initialization Scheme for Smart Cards With Reloadable Control Store

IP.com Disclosure Number: IPCOM000040284D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Abraham, DG: AUTHOR [+3]

Abstract

It is desirable to indicate the state of a reloadable control store smart card with a "state" flag byte in non-volatile store. If an application has been loaded, the flag is set to indicate that the application is present. If there is no application present, the flag is set to indicate Initial Microcode Load (IML) is required. However, when power is first applied, due to the nature of typical non-volatile store technologies, the flag bits are randomly set to 1 or 0, and it is not possible to accept the state of a simple flag as valid. This Initialization Scheme resolves this problem by testing for a predetermined unique sequence of characters in a specific location of RAM (random-access memory).

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Initialization Scheme for Smart Cards With Reloadable Control Store

It is desirable to indicate the state of a reloadable control store smart card with a "state" flag byte in non-volatile store. If an application has been loaded, the flag is set to indicate that the application is present. If there is no application present, the flag is set to indicate Initial Microcode Load (IML) is required. However, when power is first applied, due to the nature of typical non-volatile store technologies, the flag bits are randomly set to 1 or 0, and it is not possible to accept the state of a simple flag as valid. This Initialization Scheme resolves this problem by testing for a predetermined unique sequence of characters in a specific location of RAM (random-access memory). The length of this sequence determines the degree of probability that that portion of RAM is in a set state as opposed to a random state. This predetermined sequence of characters is built into the smart card ROS (read-only store). This scheme functions as follows. Immediately after power is applied, a "reset" passes control to location 000. The instruction in that location is "jump to location xyz" and check if the predetermined sequence of characters is in RAM. If the sequence is not present, it is immediately written into the RAM locations. If the sequence is present, it necessarily indicates that there has been a previous reset and the flag is set to "IML required". It is seen that this double reset s...