Electrical 389 Family
Peterbilt Motors Company 6-9
ICU/CECU Architecture
The software programming of the control module can be grouped into three main types:
Run Time (RT) - which acts as the operating system where all communication takes place.
Programmable Logic Controller (PLC) Code - manufacturer specific programmed code and software that is
developed, accessible and editable.
Vendor Module - blocks of code that are developed for specific manufacturers to allow other features to be
implemented more efficiently.
See Multiplexed Instrumentation Block Diagram (Figure 6-6).
To better understand how Electronic Service Analyst (ESA) functions and why there are current limitations on some of the
multiplexed features, by explaining what ESA can see. Currently ESA can look at all information that is communicated
between the RT and PLC Code portions of the programming. Any signals, be they inputs, outputs, or dataline signals,
sent between the RT and PLC Code are visible to ESA. These are the signals that may be monitored and simulated using
ESA.
Limitations with the ESA program are found in the communications that go to the pre-developed Vendor Modules.
Currently this information is not available for ESA to look at. That is why some features that have Vendor Module
programming, such as the odometer and the message display, are not available to monitor and/or simulate through ESA.
FIGURE 6-6. CECU Block Diagram
