Date: Fri, 21 Nov 1997 05:07:24 GMT Server: Stronghold/1.3.4 Ben-SSL/1.3 Apache/1.1.3 Content-type: text/html Content-length: 13827 Last-modified: Mon, 13 Oct 1997 21:34:00 GMT
Racom's LF Series is well suited for closed payment systems of any size as well as access control and industrial automation. It provides fast, dependable movement of data concerning transactions, authorizations, or files between people or things in motion and any kind of computer system. The LF Series consists of controllers and transponders. Transponders (located in the plastic card) are memory devices that are powered and communicate via Radio Frequency signals. Controllers provide power to the transponder and a communications channel between a computer and transponders. Because the LF transponder is completely sealed in a solid plastic package, it is impervious to nearly all environmental hazards.
In addition to products that support a wide variety of end system applications, Racom also provides products specially designed to support the evaluation, demonstration, and development of custom demonstration and end systems. See the Demonstration/Evaluation product literature for more details. We recognize that in the rapidly evolving world of Smartcard systems, your ability to demonstrate system concepts is crucial to business success. LF products and the Racom support team make developing impressive demonstration systems quick and painless and the transition to system rollout simple.
LF Controller Installation Notes
Since the LF system uses Radio signals for power and communication, performance can be degraded by nearby noise sources such as PCs, monitors, LCDs, even water coolers. Fortunately, this noise dissipates over short ranges (1 foot or less) and is easily shielded. So, if your LF system is not performing at the range you expect try moving it or shielding noise sources with aluminum foil. Be especially wary of switching power supplies, they tend to generate a great deal of electronic noise.
The host computer writes data to or reads data from LF series cards through an LF Controller. LF Controllers are available in many different configurations to support different applications. All LF Controllers consist of an antenna coil and a controller board connected by cable. The LF Controller communicates with a host by serial interface described in the next section.
The LF Controller functions as a modem between a host computer and Racom's LF series contactless smartcards. The Controller communicates with the host via RS-232C, RS-422, or CMOS level serial at 9600, 19200, or 38400 bits per second. The bit rate is set in "user FRAM" on the controller and can be changed only by command on the serial interface. The included DOS program LFMUSER can be used to change the bit rate. New bit rate settings do not take effect until power has been removed and restored to the controller. Once set, bit rate settings are maintained permanently in "user FRAM" until changed. The LF System uses a simple three wire interface. Connections are Ground, Transmit Data, and Receive Data. No other signal lines are used. The bit level protocol is asynchronous, 8-bit, no parity, 1 stop bit.
When commanded to communicate with an LF transponder (card), the LF Controller continuously produces an unmodulated 125 KHz carrier from its antenna coil. The LF card contains a coil of wire that derives energy from the controller signal. The LF card, while being powered by a sufficiently intense controller field, continuously transmits the "Configuration Word" (hex 0340) via 62.5 KHz PSK, Miller coded signal, except when responding to a command. Rather than a transmitter/receiver system, the LF card and controller should be thought of as a magnetically coupled system, like a transformer. The controller communicates with the card through only two instructions, read and write. The controller transmits by FSK modulating the powering 125 KHz field. The read instruction contains the "Customer Code" which must match that of the card, or the instruction is ignored. If the "Customer Code" matches, the remainder of the instruction, containing start block and number of blocks to be read, is received. The card then transmits these blocks via 62.5 KHz PSK, Miller coded signal.
When the controller sends a "write" instruction, besides including "Customer Code", start and number of blocks, and the data to be written, the instruction contains the "Unique ID" of the card to be written. If the "Unique ID" in a write instruction does not match that of the card, the write message is ignored. When the instruction is a "Write Verify", the written blocks are then read and compared to data intended to be written. If they match, the instruction is concluded. If a mismatch occurs, a re-write is performed beginning at the first errored block. This process is repeated, if needed, until all written data has been verified.
When the controller performs a "write with CRC", the last two bytes (4 hex digits) of the final block of the data blocks written are replaced with a CRC-16 value calculated on the data in the blocks written by that command. When the controller performs a "read with CRC", data from all blocks read (except the final two bytes, assumed to contain CRC) is used to calculate a CRC which is compared with the final two bytes (4 hex digits) read from the card. If these do not match, a CRC error is reported to the host. If they do match, the read data is transmitted to the host. Note that the card does not participate in CRC calculations in any way, except to retain the data calculated by the controller. CRC error checking is not so much a security measure as a data integrity process.
Customer Codes are assigned by Racom, and are programmed into permanent ROM on the processor in the controller. Along with Customer Codes, Unique IDs for each card are assigned by Racom, and locked irrevocably into Block 0 on each card. Racom certifies that no cards will be released without a Unique ID and Customer Code per customer order locked into Block 0. Because of this communications protocol, if a read transaction with CRC is in process, and another card were to come between the antenna and active card during the read, the controller would, at worst, return a "CRC Error" message. Generally, the communication would conclude properly. In no case would erroneous data be received, if CRC error checking was utilized. If a card was in the process of a write transaction and verified write was in use, because the data resides in host or controller buffer until verification is achieved, card contents could be garbled if another card was inserted into the field, but an error situation would be detected by the host, and data rewritten until data is correct. In no circumstances could the newly inserted card be written to or its data in any way corrupted.
The LFC-BB controller is supplied as a bare board connected to the antenna for installation in customer supplied equipment. When installed as a board in customer equipment, the customer is responsible for mounting, strain relief on cables, shielding, as well as power supply. The controller board measures 12.5 x 7.5 cm and as much as 1.5 cm high (total thickness) for the tallest components. Screw mounting holes are on 11.5 x 6.3 cm centers, centered on the board and are .3 cm in diameter. Mounting holes have no circuit foil for screw contact purposes and no foil closer than .3cm from the edge of the underside of the hole. Care should be taken that screws and mounting bosses do not contact any circuit foil or other devices on the board. The bare board should be protected from static discharges and strong electromagnetic interference. Use of jumpers on the controller board is described in the LF System Manual except for JP1, which is the manufacturing reset switch. If this pin pair is jumpered, the controller defaults to:
Baud rate 9600 bits per second
Echo on
Node Hex FF
Startup mode 0 Speaker does not beep on power up
The jumper state is read only at power up of the board, so the board must be powered down and back up before these parameters apply. Contents of FRAM regarding these parameters is not affected, so when the jumper is removed and power is cycled, previously set parameters apply. These parameters can be set via the serial interface while SF1 is jumpered using the Write User FRAM in the LFMUSER.EXE DOS program and the new values will apply when the jumper is removed and power is cycled.
The plastic enclosure is a high quality plastic enclosure protecting the controller board from dust and reasonable environmental exposure. It is NOT waterproof or unbreakable. It should not be directly exposed to weather or severe shock or impact. While the cables are strain relieved, they should not be pulled, twisted, or bent at the enclosure. Since the controller board occupies most of the enclosure, holes should not be drilled in it.
Power is supplied to both the AA and BB versions of the controller, as delivered from Racom, through a coax "barrel" type connector with 4mm outer diameter and 1mm post. The post (center) is negative (ground) with respect to the barrel (outside). The power requirement for the LF controller is regulated 12 volts +/-5%. There is no regulation of 12 volts on the board or protection from overvoltage or transients since this board is expected to be used in customer supplied equipment or with a Racom supplied external power supply. Deviation from the specified voltage will result in poor performance or damage to the controller.
Standard versions of the LF controller are supplied with attached antenna in a high quality plastic enclosure. Each controller and antenna is supplied as a tuned unit and should not be separated or performance will suffer. The standard antenna enclosure is not sealed and should not be exposed directly to weather.
The LF System operates via electromagnetic
energy near 100 KHz, below the American AM radio broadcast band.
Performance of the LF system is sensitive to RF interference such
as that produced by fluorescent lights, electric motors, and
computer monitors. These sources of interference should be
shielded or kept at a distance from the antenna. A few feet of
separation usually suffices to restore operating range but severe
sources of interference may require more distance. Adjacent
electromagnetic interference does not affect the controller
electronics board. Because metallic surfaces, particularly iron
or steel absorb and interfere with electromagnetic signals,
nearby metal or iron can severely impact performance of the LF
system. Presence of metal within 5 inches of antenna may reduce
working range.
If you have a question for the Racom Technical Support
team send us a message at techserv@racom.com
and we will respond quickly!
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