DDEC VI ELECTRONIC CONTROLS APPLICATION AND INSTALLATION
Gray Coded Using Pins 2/9, 1/11, 2/11 and Binary Coded
Gray Coded – In this mode, the engine speed set-point is received directly from two digital input
pins (LIM0 AND LIM1) on the CPC. These digital inputs are used to read the status of the two
remote PTO switches
fi
tted to the vehicle. The inputs are usually sent to the CPC from a separate
control unit hardwired directly to the CPC.
Gray code mode is the recommended interface for remote speed selection. Gray code mode has
the advantage that only one switch changes for one set-point select to the next, thus alleviating
the problem of switch bounce and non-synchronous switching.
Binary Coded – This interfacing method is designed for devices which are not capable of
generating “Gray Code” and uses the same two digital input signals (LIM0 AND LIM1). As
mentioned previously, this method has a disadvantage. When switching from speed 1 to speed
2 or from speed 3 to OFF two bits must toggle synchronously. When the contacts bounce (as
the usually do), an undesired speed set-point could be requested brie
fl
y. The preset speeds are
selected with pin 1/11 and 2/11 based on Table 5-75.
Remote PTO Enable
Input (2/9)
LIM1 (1/11)
LIM2 (2/11)
Speed Selection
Open
Don't Care
Don't Care
Remote PTO OFF
Ground
Open
Open
Remote PTO OFF
Ground
Open
Ground
Remote PTO Speed 1
Ground
Ground
Ground
Remote PTO Speed 2
Ground
Ground
Open
Remote PTO Speed 3
Table 5-75
Gray Coded Inputs
Installation for Gray Coded or Binary Input
See Figure 5-36 for the wiring of gray coded or binary input.
Figure 5-36
Remote PTO Gray Coded or Binary Input
All information subject to change without notice.
(Rev. 01/07)
5-143
7SA827 0701
Copyright © 2007 DETROIT DIESEL CORPORATION
