User Interfaces SFC6400A/SFC1450A Synthesized Frequency Upconverter
4-26 TM106 – Rev. 1.1
wait-for-SYN mode goes back into effect. If the OPCODE resides within a command message, it
defines the class of action that denotes an instruction that is specific to the device type, and is a
prefix to the DATA field if data is required. If the OPCODE resides within a query message packet,
then it defines the query code, and can serve as a prefix to query code DATA.
The Frame Sequence Number (FSN) is included in every message packet, and increments
sequentially. When the M & C computer or bus-linked equipment initiates a message, it assigns
the FSN as a tag for error control and handshaking. A different FSN is produced for each new
message from the FSN originator to a specific device on the control bus. If a command packet is
sent and not received at its intended destination, then an appropriate response message is not
received by the packet originator. The original command packet is then re-transmitted with the
same FSN. If the repeated message is received correctly at this point, it is considered a new
message and is executed and acknowledged as such.
To Next Page
Loading...