TM 11-6625-3145-14
Maintenance: Troubleshooting-318/338 Service
MAINFRAME
1. KEYBOARD TEST
Program: KBD
Function:
Power on - When power is turned on, the KBD program checks the keyboard to see if any keys are stuck in the closed
position. The MPU reads the resulting data at address E0
hex
and verifies that all data bits are low.
Troubleshooting - Refer to Figure 7-1. The keyboard generates an interrupt and sends a corresponding key code to the
MPU when any key except the STOP key is pressed. The MPU reads the key code at E0
hex
upon receiving the interrupt
from the keyboard, and blinks the corresponding rectangle in the key array on the screen. This function also provides a
check to see that each key (except the STOP key) is providing the correct key code to the MPU.
The STOP key is used to exit this program; thus the STOP key can be checked at the end of this test.
Description: Key codes are generated by the A09 board when any key is pressed. The Y-lines and X-lines of the key
matrix on the A09 board (excepting the STOP key) are connected to U300 and U310 (8-bit priority encoder, 4053BP) on
the A06 MPU/DISPLAY board through the A08 Mother board. U310 is enabled when U300 receives a key signal and
issues an INT (Maskable Interrupt) to the MPU through the CR timer circuit. The INT is controlled by U220 (NAND gate,
TC4093) on the A06 board with KBMASKP from U100 (hex D-type flip-flop with reset, 74LS174) on the A05
ROM/Threshold board .
The STOP key on the A09 board generates the NMI (Non-Maskable Interrupt) directly to the MPU through the A08 board
without decoding, though it is buffered by U200 (inverter, TC4093) on the A06 board. This signal is also controlled by the
CR timer to avoid key chattering.
The MPU reads the key code from U320 (octal buffer/line driver with tri-state output, 40H244) on the A06 board, usually on
interrupt at E0
hex
. KBCSP, which enables this buffer, is delivered from U092A (dual 2-line to 4-line decoder/demultiplexer)
on the A05 board when the MPU accesses I/O address E0
hex
.
A key code with interrupt is expected as shown in Table 7-2.
Table 7-2
318 KEYBOARD TEST KEY CODE AND INTERRUPT ASSIGNMENT
7
6
5
4
3
2
1
0
ST
0
D5
D4
D3
D2
D1
DO
ST:1 if any key is pressed, otherwise 0.
7-3
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 ...