Non-volatile memory serial number lock for electronic postage meter

Abstract

A serial number lock is provided for inclusion in a non-volatile memory of an electronic postage meter. The non-volatile memory is arranged to provide a field to accommodate a postage meter serial number. The serial number is entered into the meter at the end of the manufacturing process. The postage meter includes a routine programmed into a read only memory which is used only once during the life of the meter's non-volatile memory. The routine requires the check of a non-volatile memory lock bit location which has been set once the routine has been successfully completed. The setting of this memory location prevents reentry into the one time program. The bit is set by a true comparison of the data included in a received message with the value of the data contained in non-volatile memory. The serial number message format includes an operation binary coded decimal digit as an operational indicator. If the serial number has been entered and the operational indicator set to zero, the serial number will be changed to the value contained in the data message. If the operational indicator is a one, the firmware will examine the serial number presently contained in non-volatile memory, and compare it with the value contained in the serial number message. If the result is favorable or true, the program will set the non-volatile memory lock bit thus preventing further access to this program.