Texas Instruments 990 Maintenance Manual page 33

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945407-9701
This scoping loop may be used to test any input/output line by changing the line designations
in the SBO and TB instructions. The scoping loop is entered into the computer from the pro-
grammer panel using the following procedures:
1.
If the Model 990 Maintenance Unit is being used, set its POWER switch to the ON
position and set the MODE switch to the PANEL position. If the programmer panel
is part of the computer chassis, proceed to step 2.
2. Set the key switch on the programmer panel to the UNLOCK position.
3. If the RUN LED is lighted, press the HALT/SIE switch to halt the processor and begin
execution of the programmer panel code. When the panel is active, the RUN LED is
extinguished.
4. Press the CLR switch to clear the panel's display register.
5.
Press the ENTER ST (enter status) switch to clear .the status register in tl~ie TMS 9900.
6. Set up 1000
16
on the data display LEDs using the data entry switches. This is the
memory address where the first instruction of the scoping loop is to be stored.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
NOTE
A lighted display LED indicates a logic 1.
Press ENTER MA switch to load the memory address value 1000
16
into the memory
address register of the TMS 9900.
Press CLR to clear the displays for the next entry.
Set up the instruction code C300
16
on the data LED display using the data entry
switches.
Press MA 1 to increment the memory address value stored in the memory address register
and repeat steps
8
through 11 until all instructions and the CRU address are loaded.
Press CLR to clear the displays.
Enter 1000
16
into the displays (address of first instruction in the scoping loop).
Press ENTER PC to load the value into the program counter.
Enter 1040
16
into displays.
Press ENTER WP to enter workspace pointer.
Press CLR to clear displays.
Press RUN to begin execution of the program. The RUN LED should light to indicate
proper operation.
S-7
Digital Systems Division .