System and method for radio frequency tag group select

A method for selecting a subset of slaves that satisfy a selection criterion and then causing the selected subset of slaves to be isolated from further participation in a selecting and isolating process, said method comprising;

• storing at least one information value in each of a plurality of slaves for use in evaluating a selection criterion;
• representing a selection criterion as a selection criterion command;
• communicating the selection criterion command to the plurality of slaves, each slave of said plurality of slaves being in one of three or more difference states during the selecting and isolating process;
• processing the selection criterion command at said each slave by moving said each slave from a first state to a second state if and only if the slave is already in the first state and the at least one information value satisfies the selection criterion;
• then
• deeming said each slave in the second state to be selected;
• and
• moving the slaves in the second state to a third state so as to be unaffected by further selection criterion commands.

A state machine slave for responding to a selection criterion command from a master unit, and when selected being isolated from further participation in a selection and isolating process, said state machine slave comprising;

• first, second and third states;
• a memory containing at least one information value for evaluating a selection criterion;
• a receiving unit for receiving a selection criterion command representing a selection criterion;
• a processing unit that process the selection criterion command by moving the slave from a first state to a second state if and only if the slave is already in the first state and the at least one information value satisfies the selection criterion;
• whereby the slave is deemed to be selected if the slave is in the second state after the processing unit has processed the selection criterion command;
• and
• the slave being movable from the second state to the third state so as to be unaffected by further selection criterion commands.