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--- glossary:glossary_r [2017/02/16 10:10] – [Raspberry Pi] WortingUK
+++ glossary:glossary_r [2019/11/12 01:51] – [RFID] Bob Vetterlein
@@ Line 90: / Line 90: @@
 [[http://en.wikipedia.org/wiki/RFID|Wikipedea article]]\\
 [[glossary:thomasrfid|MERG Demonstration]]\\
+**MERG RFID systems**\\
+The tags generally used in MERG RFID systems have a 40 bit ID number, that is 5 bytes, when transmitted there is then a sixth byte added which is a checksum for data integrity. The tag readers transmit the data over a serial link using [[glossary_h#ascii_hex|ASCII Hex]]. The start of a message is STX <0x02> this is followed by the 12 ASCII Hex characters of the data plus checksum, some readers then send LF <0x0A> CR <0x0D>, and finally ETX <0x03>. This makes a message of either 14 or 16 bytes in total.\\
+The MERG Concentrator replaces the STX with a reader identification letter, A to H or I to P. For CBUS the incoming data is converted back to its original 5 bytes and checked against the checksum. These 5 bytes are then transmitted as bytes 3 to 7 of an 8 byte message. <Opcode><DN/NN Hi><DN/NN Lo><data0><data1><data2><data3><data4>
 ===== Risk assessment ======