User's Guide Part 2

CHAPTER 6 READER-HOST PROTOCOL EXTENSIONS FOR BATTERY POWERED BACKSCATTER TAGS

Memory Commands

Each tag has on-board memory that can be used for arbitrary user data storage,

or for holding sensor logging data. These commands allow this memory to be

interrogated and programmed. As always, use the ‘set mask’ command to

identify the unique tag to communicate with.

ET MEMORY

Set and Get Memory commands allow the direct manipulation and interrogation

of the tag memory. The Get Memory command will return blocks of the tag

memory, and the Set Memory command will write data to the tag memory.

Get Memory takes two parameters (length, address). Parameter one is the

number of bytes to get expressed as a single decimal number. Parameter two is

the start address of the memory to get, expressed as a single decimal number.

The maximum number of bytes that this command will return is 4Kb, i.e., 4096

bytes. The results of the Get Memory command are multiple lines of ascii data,

where each line of data will represent up to 16 hexadecimal bytes of memory. A

line of data may include asterisk characters instead of expected data – this

indicates that the request for a particular block of memory failed (usually RF

communications failure). The data can usually be extracted by repeating the

command after repositioning the tag.

Set Memory takes two parameters (address, data). Parameter one is the start

address of the memory to set, expressed as a single decimal number. The

second parameter is an ascii string of hex bytes, up to a total of 64. This process

is usually a slow process so the progress of the write operation is displayed on

screen as each memorypacketsize bytes are written.

Note: Memory is transferred to and from the tag in blocks of memory defined by

the memorypacketsize command. The smaller the packet (i.e. 1 or 2 bytes) the

smaller the transmission rate but also the smaller the error rate. Likewise the

higher the packet size (i.e. 16 bytes) the higher the transmission rate but also the

higher the error rate in a noisy environment.

Example

Command

Response

>Get Memory 20, 0

Memory@0000 = AF 00 A5 17 59 01 01 01 01 01 A5 0A 00 00 A5 80

Memory@0010 = 16 80 16 80

Command

Response

>Set Memory 0, 01 02 03 04 05 06 07 08 09 0A 0B

Set Memory @0

Set Memory @4

Set Memory @8

Set Memory Success