TM 11-6625-3145-14
Maintenance: Troubleshooting-318/338 Service
Step 2. A word is read from a diagnostic cell and checked with the expected word 55. If it is not equal to word 55, an error
message is displayed and the MPU is halted.
Step 3. If the previous test was successfully completed, the word AA is written into that cell. Then a word in the same cell
is read back and compared with AA. If it is not equal to AA, an error message is displayed and the MPU is halted.
Step 4. Steps 2 and 3 are repeated for all RAM addresses.
Troubleshooting - None.
Description: The read and write operation on the Display RAM U515 (16 K-bit static CMOS RAM, uPD446/HM6116P) on
the A06 MPU/Display board is completely controlled by Display Controller U500 (display controller, MB62110) on the A06
board.
The MPU reads/writes data from/to the Display RAM through U525 (octal bus transceiver, 40H245) on the A06 board,
which is enabled by the Display Controller and the data direction is specified (read or write) by the MPU’s read signal. The
addresses to the Display RAM are supplied by both the MPU and the Display Controller, however the addresses from the
MPU are sent to the Display Controller and the Display Controller gates these signals to the Display RAM.
If there is competition between the MPU and the Display Controller for access to the Display RAM, the Display Controller
forces the MPU to wait until it completes the current read operation by asserting the WAIT signal to the MPU.
The MPU checks the Display RAM with a checkerboard marching pattern. The read and write sequences are already
mentioned in the preceding Power on paragraph. If the data read is incorrect, the MPU will display an error message.
5.
SYSTEM RAM TEST
Program
Function
Power on - SYSTEM RAMs are checked with a checkerboard marching pattern from addresses F000 through F7FF and
from F800 through FFFF.
Step 1. The word 55 is written into all RAM addresses.
Step 2. A word is read from a selected diagnostic cell and checked against the expected word 55.
If it is not equal to word 55, an error message is displayed and the MPU is halted.
Step 3. If the first test is successfully completed, the word AA is written into that cell. Then the word in the same cell is
read back and compared with AA. If it is not equal to AA, an error message is displayed and the MPU is halted.
Step 4. Steps 2 and 3 are repeated for all RAM addresses.
Troubleshooting - None.
Description: RAMs U400 (F000-F7FF) and U401 (F800-FFFF) on the A06 MPU/Display board used by the MPU are called
the System RAM. The MPU Data Bus (DO-D7) and the partial MPU Address Bus (AO-A10) are directly connected to
these RAMs.
7-8
Summary of Contents for 318
Page 119: ...318 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 182: ...338 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 253: ...318 ___________________ TROUBLESHOOTING TREES ...
Page 344: ...338 TROUBLESHOOTING TREES ...
Page 517: ...TM 11 6625 3145 14 318 338 4434 923 318 Block Diagram ...
Page 518: ...TM 11 6625 3145 14 318 338 4434 924 338 Block Diagram ...
Page 519: ...TM 11 6625 3145 14 318 338 4434 925 318 Acquisition Module Wiring Diagram ...
Page 520: ...TM 11 6625 3145 14 318 338 4434 926 318 338 Mainframe Wiring Diagram ...
Page 521: ...TM 11 6625 3145 14 318 338 4434 926 338 Acquisition Module Wiring Diagram ...
Page 522: ...TM 11 6625 3145 14 318 338 4434 928 Figure 9 1 318 A01 Input A Board Component Locations ...
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Page 528: ...TM 11 6625 3145 14 Figure 9 3 318 338 A03 ACQ Control Board Component Locations ...
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Page 542: ...TM 11 6625 3145 14 Figure 9 8 318 338 A10 CRT Board Component Locations ...
Page 544: ...TM 11 6625 3145 14 Figure 9 9 318 338 A11 Inverter Board component Locations ...
Page 546: ...TM 11 6625 3145 14 Figure 9 10 318 338 A12 Regulator Board Component Locations ...
Page 551: ...TM 11 6625 3145 14 Figure 9 12 338 A01 Input A Board Component Locations ...
Page 553: ...TM 11 6625 3145 14 318 338 SERVICE ...
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Page 555: ...PIN 058584 ...