Sullair SUPERVISOR CONTROLLER Instruction Manual

Section 6
CONTROLLER COMMUNICATION
PROTOCOL
26
• There are no extra communications for monitoring. Since each machine sends its
status every second, the monitor does not need to send messages. However, the
monitor may send messages to get other status or change parameters.
• The monitor does not need to be continuously connected. A monitor may be
connected or disconnected at any time without affecting the system operation.
6.3 RS-485 SERIAL CHANNEL
The half-duplex RS-485 serial connection is a “party line” type channel, meaning any
device on the channel may transmit or receive over the same connection. The
transmitters and receivers are differential type that use two wires and a ground. These
components have excellent noise immunity because the receiver measures the relative
voltage between two signals, not between a signal and ground (as is the case with RS-
232 channels). If noise occurs on both lines it will be rejected by the receiver.
The ground is used to keep the receiver from floating too high above the transmitter. A
“one” signal is transmitted as 5 volts on the + line and 0 volts on the - line. A zero” signal
is transmitted as 0 volts on the + line and 5 volts on the - line. The transmitters are tri-
state, meaning they can drive the transmission line to a one (5 volts), zero (0 volts) or be
turned off (high impedance). All transmitters except one must be in tri-state mode. This
prevents damage to the transmitters and the transmission from being garbled.
6.4 TIME SLICING OF THE RS-485 SERIAL CHANNEL
When the sequencing mode is set to HOURS or COM ID# the machines will broadcast
their status (net status message) about once per second. Time is sliced into periods (up
to 17 maximum), one for each machine and one for a monitor. A machine will only send a
net status message during it’s time slice (see Table 6.1 below).
Table 6.1 RS-485 Time Slice
Time Slot COM ID# Time out
0 Monitor 0.6 sec
1 1 0.1 sec
2 2 0.1 sec
3 3 0.1 sec
…… …
The number of machine time slots is determined by the LAST COM parameter. The
controllers establish the current time slot by either receiving messages or timing out. The
last member sends a monitor enable message, which begins slot 0, without waiting for
higher number slots. During time slot 0, a monitor may send a message, typically a
status request or parameter change message. A message that is sent by the monitor
may need a response from one of the machines. This response must come before the
time out period (0.5 sec).
When a machine comes on line, it waits for an initial timeout period of 1.5 + 1.5 times the
COM ID# seconds. If a monitor enabled message is received during the initial timeout
period, then the time slot is established by the machine’s COM ID#. If no messages are
received within the initial timeout period, the machine initiates a new cycle.

Sullair SUPERVISOR CONTROLLER Specifications

General

Brand	Sullair
Model	SUPERVISOR CONTROLLER
Category	Controller
Language	English