Changing one of many access codes upon removal of ignition key
US5252965A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 15, 1991 |
| Grant date | Oct 12, 1993 |
| Priority date | — |
| Expiry date | Mar 15, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG07C2009/00793
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A system for unlocking any of several vehicles by a passive electronic key coupled to base units in the vehicles by a radio link uses short range LF transmission for signals to the key and VHF transmission for signals to the base units. The key has a ferrite antenna connected to a receiver comprising a comparator. When an operator pulls the door handle, codes stored in the base are transmitted to identify any authorized key within the range. The key has a memory partitioned into separate blocks for different base units and another block for a scratchpad memory. A state machine stores the block addresses and controls access to the blocks according to the transmitted codes. When a block is accessed, a secure ID in the block is sent to the base unit to verify that the key is authorized to unlock the vehicle. The ID can be updated upon command from the base unit using the same codes to assure that an authorized unit is receiving the new ID. The new ID is written to the scratchpad, verified for correctness, and the scratchpad address is exchanged for the address of the block containing the old ID. Auxiliary data specific to the vehicle or to the user of the electronic key may also be st…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.