Escort LRP2000 manual 127, Command/Response Size, Example Ascii Command, Fill Tag

RFID Communications

If the controller encounters a fault, it responds with the following:

	Number of
Field	ASCII	Content
	Characters
Header	2	<STX><STX> (02H, 02H)
Response Size	4	Packet length in bytes excluding the header, response size, checksum and
		terminator bytes.
Error Flag	2	FFH
Error Code	2	Hex error code
Checksum	2	Optional checksum
Terminator	1	<ETX> (03H)

Most RF operations also require additional parameters and data that will be included in the command stream between the command code or echo and the terminator. The header and terminator are always STX and ETX respectively. Any other field value is in ASCII hex notation. Allowed values: '0'-'9', 'A'-'F'. Example: the value ABH (decimal 171) in ASCII protocol is transmitted as a two-character string «AB», i.e. the two bytes: 41H 42H (ASCII values for 'A' and 'B'). The hex value of the hex digits given in ASCII are: '0'- '9' = 30H - 39H, 'A'-'F' = 41H-46H. The sequence for each command is given with the response format in the preceding section. Referring to the ABx Fast command you can structure the ABx ASCII commands by using ASCII values for each digit of the hex values, excluding the header and terminator that are already ASCII characters.

Command/Response Size

The ABx ASCII requires the length of the packet be included in the command. All parameters and data between the command size and the terminator or checksum byte must be accounted for in the packet size word. This includes all command codes and parameters such as field definition for Block Read/Writes. The packet size remains the same with or without the checksum.

Checksum

The optional checksum must be enabled from the operating mode menu to be available. The checksum is calculated by adding all the byte values (not the ASCII translation values) in the packet (less the values in the header, checksum if present, and terminator), discarding byte overflow, and subtracting the byte sum from FFH.

Example ASCII Command, Fill Tag

This command fills the specified number of cells from the specified start address with the specified value. Block size = 0 means filling to the end of the memory. The command takes the same form as the ABx Fast command.

Field	Content
Header	<STX><STX>
Command Size	Packet length in bytes excluding the header, command size, checksum, and terminator bytes. Given as
	four ASCII character value. 0008H for this command
Command	<30H><34H> (04)
Start Address	4	ASCII character value for the starting tag address
Fill Length	4	ASCII character value for the length of the fill in number of bytes
Timeout	4	ASCII character value for timeout in 1 ms units. (1EH - FFFEH)
Data Value Byte	2	ASCII character value for 1 byte of fill
Checksum	2	ASCII character value for Optional Checksum
Terminator	<ETX>

127 LRP2000 Passive Reader/Writer