JLG 680S, Service And Maintenance Manual

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SECTION 6 - JLG CONTROL SYSTEM
3121234 6-25
6.4 CANBUS COMMUNICATIONS
CANbus: CAN (Control Area Network) is a two wire differential
serial link between the Platform Module, Ground Module,
Boom Length Angle Module and the Chassis Module provid-
ing bi-directional communications.
Two-wire: One wire (red) is driven high (5v) and the other low
(black) (0v) to send a signal; both wires ”float” (2.5v) when no
signal is being sent.
Differential: Any electrical line noise can affect the high or the
low wires but never both, so communications is not corrupted.
Serial Link: Messages are being sent bit by bit along the wires;
the high bus speed allow all modules to be constantly
updated around 20 times per second. Typical traffic is 300 -
500 messages per second.
A complete CANbus circuit is approximately 60 ohms, which
can be verified at the ”T” fitting inside the ground station or
below the BLAM. Each individual circuit from the modules is
approximately 120 ohms.
The GROUND MODULE (UGM) is the master system controller.
Most functions are dispatched and coordinated from this
module, The PLATFORM MODULE handle sub-tasks. All charac-
terized information (values) are stored into the ground mod-
ule (i.e. Personalities or Calibrations).
Interlocks : Any device that sends an electrical input. (For an
example a limit switch, proximity switch, etc).
Platform Leve l: The GROUND MODULE stores the default val-
ues and handles interlocks. The PLATFORM MODULE reads the
sensors mounted on the platform assembly and controls the
Level Up / Down valves to maintain setpoint sent from the
GROUND MODULE.
Steer : The GROUND MODULE stores crack points and sends
desired drive direction, steering mode and axle extend/retract
commands. The PLATFORM MODULE reports the steering
switch position to the GROUND MODULE.
Drive: The GROUND MODULE stores crack points, sends com-
mands for each drive pump. (Command is computed from
drive joystick input, interlocks, wheel angle, etc).
Lift, Tele, & Swing : The GROUND MODULE stores default val-
ues and handles interlocks and calibration information. Lift,
Telescope and Swing commands are dependent upon inter-
locks through out the machine. Boom angle, length and swing
are controlled by the GROUND MODULE.