(d)
Low battery condition occuring in a battery back-up RAM will be annunciated by the fault code MMF (Maintenance Module Fault) at power up and/or BITE check.
(14)
Exceedance Data Display
(a)
The unmarked BITE test button is used to display exceedance data stored in the individual microprocessor systems prior to removal of power. Once the electrical power is removed, the system shuts down and the exceedance data will be lost from the volatile memory and will no longer be accessible by using the BITE button.
(b)
Two successive actuations of the BITE pushbutton within two seconds initiates an exceedance display. Upon initiation, the digital display for that parameter (N1, N2 or EGT) that has recorded an exceedance condition will display the highest exceedance value experienced since power application. The value(s) are displayed for 2 seconds. The affected display(s) then display the accumulated time in seconds of the over-limit values that have existed since power application. This value(s) is displayed for 2 seconds and during this time the display annunciates SEC vertically on the far right-hand LED counter. The displays then return to the pretest condition upon release of the BITE button.
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(c)
If no exceedances have occurred during the engine run/flight and the exceedance display is requested, the engine indicators will continue to display current parameter values and will not change. The indications will only change when an exceedance value has been recorded and the power to the EIS has not been removed. Removing the power (for 10 seconds or more) before requesting the exceedance display will reset the exceedance values to zero.
(d)
Exceedance data display, like BITE test, can only be performed when both N1 values are below 10%.
(15) Interrogation and Erasure of Exceedance Data
(a)
The exceedance data can be interrogated and erased when the airplane is on the ground. The EIS Primary Display unit exceedance memory INTERROGATE and ERASE discrete inputs and ARINC 429 outputs are accessible via the EIS test connector D10146, which is located on a stanchion of the E2 rack, at station 347 in the E/E compartment.
(b)
Any suitable ARINC 429 bus reader can be used for retrieval of the exceedance data, this can be accomplished by connecting an ARINC 429 bus reader to the EIS test connector (D10146) and interrogating the exceedance memory. A bus reader with storage/print capability will assist in the data retrieval. The data retrieval (dump) will start with the left engine, starting with N1, then EGT, N2 and fuel flow. If no data is held for the parameter a single "exceedance" transmission with a null data field will be transmitted for that parameter.
(c)
A ground applied to the INTERROGATE discrete (pin 3 of D10146) will cause the exceedance memory to be output to the ARINC 429 bus. The data is output starting with the most recent block of data and ending with the oldest. The data is available at pins 1 and 2 of D10146 approximately 20 seconds after the INTERROGATE discrete is applied.
(d)
Three to five minutes after the initiation of data retrieval, the exceedance memory may be erased. Interrogation of the exceedance memory must be done before you erase the exceedance memory.
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EIS Secondary Display Schematic Diagram
Figure 5
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