Teledyne API Model 200A NOX Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
Like the display, the overall functioning of the CPU can be confirmed by a simple test.
1. Locate the CPU board on the mother board by referring to Table 2-2-5.
2. Power the instrument on.
3. Locate the red LED at the top left edge of the board.
4. It should be flashing at a frequency of about once per second.
5. This flashing indicates the board is powered up and is executing instructions.
Testing and operation of the CPU RS-232 port is described in Section 9.3.2. It is possible for the
UART driver chip to malfunction in either or both of the input or output ports.
9.3.1.3 Front Panel Keyboard
The keyboard consists of 8 keys and 3 LED's. Key strokes are sent to the SBC40 computer's
parallel port. The computer software detects the key strokes via interrupts. The bottom line of the
display consists of 40 characters which is divided into 8 - 5 character fields. Each field defines
the function of the key immediately below it. The definition of the keys is variable and depends
on the menu level of the software.
To check the operation of the keyboard, each key should perform an operation indicated by its
current definition shown on the second line of the display.
Example #1 - testing key#1 (left most key).
At the top level menu key #1 is defined as the TEST function. Pressing this key should cause the
middle field of the top line of the display to show the various test functions.
Example #2 - testing key #8 (right most key). At the top level menu key #8 is defined as the
SETUP key. pressing key #8 should cause the SETUP menu to be displayed.
Example #3 - If the 5 character field above any key is blank, the key is not defined, pressing the
key has no effect.
9.3.1.4 Front Panel Status Indicators
The 3 status LED's indicate several functional states of the instrument such as calibration, fault,
and sample modes. The state of the LED's is controlled by 3 lines on the parallel port of the
SBC40. Functioning of the LED's can be checked by:
1. Turn off the M200A power.
2. While watching the LED's, turn on the instrument power.
3. When the power comes up, the computer momentarily applies power to all 3 LED's. If all
the LED's are observed to light, they are working properly.
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