User's Manual

Table Of Contents
Because ABx Non-separation removes the termination bytes that indicate
the end of the message, the programmer must remember how many bytes
the command asked for. In the ABx Fast response there is always a
checksum byte included in the data array (00H if checksum option is dis
-
abled).
The ABx Non-separated selection works across all device types (generic &
polled) types.
A handshake word (2 bytes) is required in the beginning of the command
and response of every single device type (generic and polled). The polled
mode uses this word as a handshake field regardless of the ABx separation
mode chosen and must be considered when calculating the size of the mes
-
sages. In essence ABx non-separated always adds 2 bytes (1 word) to the
start of both command (produced) and response (consume) fields.
The HMS830 ABx Non-separated command OK responses are protocol
independent of protocol in fact they are the same with the exception of the
optional checksum byte within ABx Fast.
Polled Commands in ABx Non-separation Mode
In Polled mode, the PLC first Word lower byte raises a single REQ bit to
send the message.
For example, this would cause AA050000000607D0FFFF (a read command
ABx standard style) to be executed. Generic now has the first Word (word
zero) in the command as a header. This means that both types, polled and
generic, have the same response format.
ABx Fast protocol commands will also have a handshake word as the
header. If no header is desired then do not use the ABx Non-separated mode.
Error Management
ABx Non-separated polled response is the same as the standard response
with regards to the first Word. The single exception here is the handshake
byte has the most significant bit being set to 1 indicating that the command
had an error response. This ERROR bit in the response saves the program
from parsing the message to see if the retry is necessary to read a tag. When
a response is not an error response this bit is left to 0.
Copyright © 2000 Escort Memory Systems
LRP830-Series Long-Range Passive Reader/Writer
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