User's Manual

MPR series User’s Manual: Draft version 0.95 11/4/04 page 36
1.6.5 Messaging Protocol
1.6.5.1 Protocol Description
• Host – Reader communications follows a Request-Response protocol.
• The Host sends request packets, and the Reader sends Responses. The Reader never sends
unsolicited traffic.
• Every properly received request is acknowledged with at least one response packet.
• A response may consist of more than one packet.
• Bytes received before a proper SOF (Start of Frame) byte and packets with CRC errors are
ignored.
• There is no explicit message termination.
• The Length byte must be used to determine the location of CRC, and therefore, the end of packet.
• Maximum data section length is 64 bytes for host Request Packets.
• Maximum data section length is 256 bytes for reader Response Packets.