Section D. The CPU Board
What the CPU Does

!!!!Section D Applies to Both the N-8242 CPU Assembly and the N-8915 CPU Assembly.

Figure 1

The CPU board is considered the "Brain" of the electronic head. The CPU board contains one microprocessor to control all of the basic dispenser functions. These functions include:

1. Processing pump handle signals

2. Processing pulser signals

3. Accumulating and storing sales data

4. Running diagnostic routines

5. Activating solid state relays which control solenoid valves and pump motor circuits

An extension bus is provided to expand the available peripheral space and functions (DCA interface, Local Preset display, etc.) of this board.

            HOW TO CORRECT GENERAL PROBLEMS ON THE CPU

     PROBLEM                  CAUSE                  ACTION

1. Dispenser is locked  a. Pump not grounded   a. Use proper
 or looses memory.       with a 12 gauge        grounding
                         green earth ground     procedures.
                         wire.
                      b. An RC network       b. Install RC
                         missing from the       network.
                         auxiliary relay coil.
                      c. Electronic power is c. Verify elec-
                         not a clean isolated   tronic power.
                         120VDC circuit from
                         main panel to the 
                         dispenser.
                      d. Loose connection of d. Resolder 
                         the 3.6 NiCad bat-     connection and/
                         tery on CPU board      or replace 
                         or low voltage         battery.
                         (below 2.2VDC)