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Host-to-Reader Communication

54 Overview of the Communication Protocol

The fields are summarized in the following table.:

Field Length Description

Header (Hdr) 1 byte Defines the start of the packet. Equal to 0xFF

Data Length (Len)

1.Minimum packet length is 5 bytes; the maximum packet length is 255 bytes.

1 byte Defines the length, N, of the data field contained in the

packet.

Command 1 byte Specifies the command that the reader is to execute.

Data N bytes

(0 to 250)

Defines the binary data required by the reader for use with a

command. This could, for example, represent transponder

data to be written. The length, N, can vary between 0 and

250 bytes.

CRC-16 Checksum

(CRC HI, CRC LO)

2 bytes CRC-16 checksum (high order byte first). CRC polynomial is

CCITT CRC-16, with a preload of 0xFFFF. This does not fully

specify the operation of the CRC, see

CCITT CRC-16 Cal-

culation.

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Thingmagic M5e-Compact Bedienungsanleitung Seite 54