TM 11-6625-3145-14
Theory of Operation-318/338 Service
A06U 130 is the TV timing generator for the display control of the 318 and the 338. It generates C-SYNC (Composite
SYNC), HD (Horizontal Drive), VD (Vertical Drive), and CBL (Composite Blanking) from the output signal of A06U120B
(244.4 ns clock).
A06U134 gates A, B, and C generate the blinking clock signal (about 30 Hz) for A06U500. A06U500 is a display control IC;
it consists of a display counter, address bus multiplexer, Z-axis generator, and Z-axis controller. The display counter
determines the location of the FONT in the screen, and either blanks or unblanks the display.
The address bus multiplexer selects the output of either the display counter or the MPU address for the display RAM
(U515).
The Z-axis generator generates the Z-axis signal from the output of the character ROM (A06U530). The Z-axis controller
controls the Z-axis signal (inverse, blank underscore, or blinking) and generates the trace edge for timing displays.
The data bus transceiver stage of the display controller consists of A06U510 and A06U525. This stage controls the data
communication between the MPU and the display RAM, and allows the MPU to either write data into or read data from the
display RAM while the display RAM address is accessed by the MPU.
Character latch A06U520 latches the 8-bit data read-out from the display RAM. The latched data is maintained for seven
display clock cycles to achieve seven dots of display per character. Data input to the character latch stage is provided and
latched on the positive-going edge of the character latch clock.
Character ROM A06U530 provides the character fonts which allow a variety of displays. Each character font in this ROM
is composed of a 7 X 8-dot matrix and is selected by the 8-bit signal from the character latch stage and a 1-bit signal
(CROM) from the A05 board. The CROM bit selects either a parallel-mode character or a serial-mode character.
Each of the eight lines of a character font are selected by the line select signal from the display counter. The seven dots
on each line of a character font are read out from the ROM when that character is addressed. The 7-bit parallel output
data is loaded into shift register A06U500 (Z-axis generator) by the clock and is shifted out in serial format to be used as a
Z-axis signal.
A06U505, A06U540, and A06Q550 comprise the video generator and CRT driver. The video generator is a 2-bit (4-level)
Digital-to-Analog (DIA) converter.
The output level of the DIA converter is shown as follows:
Video Out
C-SYNC
INV Z
Glitch
Volts
H
X
X
-0.3
L
L
L
0.7
L
L
H
0.4
L
H
X
0
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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 ...
Page 526: ...TM 11 6625 3145 14 ...
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 ...
Page 554: ......
Page 555: ...PIN 058584 ...