01 March 2003 Foundation fieldbus high-speed Ethernet—just the
facts By George Thomas and Perry Marshall Foundation fieldbus
(FF) comes in two flavors. H1 (Hunk 1) is a low-cost bus for
devices at the lower level, operating at lower speeds like
sensors, actuators, and transducers. High-speed Ethernet (HSE)
is for interconnecting subsets of low-level devices. It is a
protocol that allows a controller to recognize a rich set of
configuration and parameter information (device description)
from devices that have plugged in to the bus. FF HSE
encapsulates the H1 protocol inside of TCP/IP, in much the same
way Modbus/TCP encapsulates Modbus protocol and transmits via
Ethernet. WHAT'S THE DIFFERENCE? H1 segments use standard 4–20
mA wiring and operate at 31.25 kilobits per second. H1 is a
digital replacement for the old 4–20 mA standard. HSE operates
on standard Ethernet links, typically at 100 megabits per second
(Mbps). 10-Mbps HSE devices are available as well. FF H1 links
local islands of transducers and actuato