Escort LRP2000 manual Conventions, Command protocols

6 RFID Communications

6.1 Introduction

Conventions

In this manual, numbers expressed in hexadecimal are appended with “H.” For example, the decimal number 10 is expressed as “0AH” in hexadecimal. The addresses of the bytes of read/write memory within an RFID tag are numbered from 0 to N, where N is one less than the number of read/write bytes in the tag. The number of read/write bytes is equal to the Block Size multiplied by the Number of Blocks.

Command protocols

The LRP2000 offers three possible command protocols: ABx Standard, ABx Fast, and ABx ASCII. The commands in all three protocols have the same basic structure. RFID Command protocols do not affect the LRP2000 to tag communications.

ABx Standard is a word-based format and shares a common syntax with most existing RFID systems produced by Escort Memory Systems. ABx Standard was designed for PLCs that handle word-based data better then byte-based data.

The ABx Fast and ABx ASCII protocols are byte-based packet structures. ABx Fast permits command execution with fewer total bytes transferred. Escort Memory Systems recommends ABx Fast with checksum enabled because of faster command execution and increased error detection.

Commands are comprised of a header, a number of parameters, and a command terminator. The headers and terminators are unique to each protocol, but are the same for every command within one protocol. For example, in ABx Standard, every command begins with the one-byte header “AAH,” and ends with the two- byte terminator “FFFFH.” In ABx Fast and ABx ASCII, every command begins with the 0202H, and ends with 03H for the default configuration setting. The header and terminator can be changed in the configuration settings menus.

Like the commands, the responses from the controller comprise a header, a number of response codes and data, and a response terminator. The headers and terminators are the same for the responses as they are for the commands. The ABx command set is made of three subsets: the single-tag commands, multi- tag commands, and user I/O commands. The single-tag commands perform read/write operations on exactly one tag in the range of the antenna at a time. The presence of more than one tag within the range of the antenna may cause RFID communication errors. To avoid these errors, the multi-tag commands allow for simultaneous communication to and from multiple tags within the reading range of the antenna.

The user I/O commands do not communicate with RFID tags. They simply interrogate the status of the inputs wired to the unit, and set the status of the outputs.

LRP2000 Passive Reader/Writer 55