Model 7002Switch System Instruction Manual - Advanced Test ...

MaintenanceTo review the error, press ENTER. The display will show thetest which failed. For further information on the failure, pressINFO. Refer to the appropriate test numbers below for furtherexplanations. The following discussions also suggest themost likely board failure for each type of error. You may alsofind it helpful to refer to the schematic diagrams.Test 100 (EPROM)Failure of Test 100 suggests a digital board error.All ROM bytes (except for the checksum bytes) are read, achecksum is calculated and compared to the stored checksum.A fault of this test indicates that one or more ROM locationscannot be read properly. Check U105 and associated logic.Test 101 (RAM)Failure of Test 101 suggests a digital board error.This is an abbreviated version of power-on RAM testing.Memory locations are written and read back. It is highly unlikelythat this test will ever fail. A unit with faulty RAM willprobably fail the power-on memory test or lock up intermittently.Check U107, U108, and associated logic.Test 102 (EEPROM)Failure of Test 102 suggests a digital board error.An attempt is made to read a byte of information from the24C16 configuration EEPROM (U112) and an acknowledgesignal is verified. A fault in this test indicates a problem withthe 24C16 component or associated signals. The test doesnot verify the validity of configuration information stored inthe EEPROM. Check U112.Test 103 (Digital I/O)Failure of Test 103 suggests a digital board error.NOTEWith some firmware revisions, the digitaloutput tests (103.1 through 103.4) will notpass if the built-in resistors are not present.(See paragraph 4.15.1).Digital I/O on the Model 7002 consists of four opencollectoroutputs, and one TTL-level input. Outputs originatefrom the 68302 microprocessor PA4-PA7 (U110). PA4drives OUT1, PA5 drives OUT2, etc. These signals arebuffered by a 2596 open collector driver (U109).Digital input is buffered by protection circuitry(CR112,CR113, R136, R137) and read by the 68302 at PB8.Tests 103.1-103.2 ⎯ Digital output bits 1-4Failure of Tests 103.1-103.2 suggests a digital board error.These tests make use of the fact that the 68302 Port A registersare bidirectional even though in normal use they are programmedas outputs only.Diodes and resistors are connected around the 2596 so thatdigital output 1 feeds back to PA5, 2 feeds back to PA6, 3 toPA7, and 4 to PA4. (Note that signal numbers are scrambledat the 2596 open collector driver. The numbers in the abovedescription refer to the digital output signal numbers, not tothe numbers on the 2596.)During Test 103.1, PA4 and PA6 are programmed as outputs,PA5 and PA7 are programmed as inputs. As PA4 (digital output1) is toggled high and low the signal is verified at PA5.During Test 103.2, PA5 and PA7 are programmed as outputs,PA4 and PA6 are programmed as inputs. As PA5 (digital output2) is toggled high and low the signal is verified at PA6.Tests 103.3-103.4 ⎯ Digital outputs 3 and 4 (test similarto 103.1-103.2).Success of these tests assures the basic functionality of PA4-7, the 2596 and associated components. A failure may becaused by shorted or defective components or by open orshorted PC board traces.Tests 103.5 ⎯ Digital InputFailure of Test 103.5 suggests a digital board error.This test verifies that the digital input signal is pulled high atPB8 of the microprocessor (U110). Success of this test doesnot guarantee functionality. A failure may be caused by a defectivecomponent or a short circuit.Test 104 (IEEE-488 Test)Failure of Test 104 suggests a digital board error.7-14