User`s guide

2: FMP Protocol Summary
DC 900-1339H 31
An example of an unstructured asynchronous feed is SIAC’s Ticker A feed.
2.1.3 Isochronous Market Feeds
The isochronous protocol is asynchronous character framing that is clocked by an
external source (such as a modem). FMP receives these feeds in the same manner as the
unstructured asynchronous feeds except that the line mode option must be set to
isochronous and the clock source option must be set to external. See the diagram in
Section 2.1.2.2.
2.1.4 Bonneville Market Feed
The Bonneville feed is an 8-bit asynchronous broadcast feed generated by the
Bonneville Telecommunications Company. Each incoming packet starts with a fixed
size header that contains the count of the data bytes in the packet. The following is an
example of a Bonneville feed packet:
The frame check sequence (FCS) for each packet consists of two bytes. The first FCS
byte is calculated by taking the “exclusive or” of every other byte beginning with the
byte count field. The second FCS byte is calculated by taking the “exclusive or” of every
other byte beginning with the VCN high byte. For more information about the
Bonneville packet format, refer to the Packet Definition and Description document
available from the Bonneville Telecommunications Company.
2.1.5 Character Codes
The Simpact FMP software can transmit and receive data in either the American Stan-
dard Code for Information Interchange (ASCII) character set, Extended Binary Coded
Decimal Interchange (EBCDIC), or five-level or six-level Baudot code depending on
the setting of the data translation option. The data transferred between the client pro-
Start
Flag
Address
Flag
Byte
Count
VCN
High
VCN
Low
End
Flag
FCS2
FCS1
Data Bytes