ib technology

4

Supported transponder types

The Micro RWD EM4102 version is designed to read data from EM Marin EM4001/EM4102

transponder types and compatible read-only tags with the correct header, data and parity bit

structure (direct ASK modulation, Manchester coded with data rate of RF/64).

The operation of the Micro RWD and EM4102 transponders is described in more detail at the

end of this document.

In Microchip MCRF200/123 Reader mode the RWD supports the MCRF200/123 read-only

transponder with 16-byte memory, 0x802A header and direct ASK modulation, Manchester

coded with data rate of RF/64.

Note that to maintain compatibility with other RWD systems the identification codes

used for the Auxiliary outputs are 4-byte (32-bit) value:

Bytes 1-4 of EM4102 memory (least significant 4-bytes, ignoring first byte)

Bytes 12-15 of MCRF200/123 memory (least significant 4-bytes)

Serial Interface

This is a basic implementation of RS232. The Micro RWD does not support buffered

interrupt driven input so it must control a BUSY (CTS) line to inhibit communications from

the host when it is fully occupied with card communication. It is assumed that the host (such

as a PC) can buffer received data. This CTS signal must be connected to the host computer

communication port to allow “hardware handshaking” or the host driver software must check

the CTS signal and only send commands/data when it is in a LOW state. The CTS signal is

pulsed LOW for a 6ms period each polling cycle. The host computer must wait for this LOW

signal and then send the command and data.

The CTS line remains in a LOW state while the command and data bytes are being received.

After the last byte of data the CTS signal “times out” for 6ms and returns HIGH.

This 6ms “window” every polling cycle allows the host computer to send a single command

and associated data to the RWD. Please note that only one command and it’s corresponding

data bytes can be sent during a CTS LOW period, the command and data bytes must be sent

with no gaps between, if there is a pause of more than 6ms between bytes then “time out”

occurs, the CTS line returns high and the command fails (flagged as RS232 error). The CTS

signal idles in this HIGH state (to inhibit host communication) until the next polling cycle

begins.

The communication baud rate is 9600 baud, 8 bits, 1 stop, no parity. The RWD Tx, Rx and

CTS signals are all TTL level and can be converted to +/-10v RS232 levels using a level

converter device such as the MAX202 (note the inversion of the TTL levels).

The Micro RWD EM4102 LP (low-power) version has been specifically designed to

operate with very low average power consumption but still remain responsive to cards

entering and leaving the field and be able to read large amounts of data as quickly as

possible.