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TM 11-6625-3145-14
Theory of Operation-318/338 Service
318/338 A07 SERIAL, NON-VOLATILE MEMORY, RS232C <17> <18>
SERIAL INPUT <17>
The serial input circuit consists of an input comparator, an offset adjustor, and a clock level translator. It provides serial
data and external clock signals for serial operation. A simplified diagram of the serial input circuit is shown in Figure 4-11.
Input Comparator. The input comparator consists of an FET input pre-amp (A07U100) and a comparator (A07U110).
Serial data applied to pin #3 of A07U100 is amplified two-and-one-half times and output on pin 6. Pin 6 is connected to pin
2 of A07U110. The threshold voltage is applied to pin 3 of A07U110. Comparator A07U110 compares the serial data
input at pin 2 with the threshold voltage input at pin 3. If the serial data input voltage is higher than the threshold voltage,
A07U110 issues a high TTL output at its pin 7.
Offset Adjust. The serial data offset is adjusted by one potentiometer, A07R23. Input serial data is monitored at TP10,
and threshold voltage is monitored at TP11. The data 0 volt level can be adjusted to equal the threshold 0 volt level by
tweaking A07R23.
Clock-Level Translator. The clock level translator is comparator A07U111. The ECL-level external clock signal from the
A02 Input B board connects to pin 2 of A07U111, and the input at pin 3 of A07U111 is set at -1.25 V. Comparator
A07U111 compares the external clock signal at pin 2 with the -1.25 V at pin 3. If the external clock voltage is higher than -
1.25 V, A07U111 will issue a TTL output at pin 7.
NON-VOLATILE MEMORY <17>
The non-volatile memory circuit provides battery backup operation for the non-volatile memory. It consists of the threshold
voltage detector, the chip select controller, the battery switch, the battery voltage checker, and a random access memory.
Threshold Voltage Detector. The threshold voltage detector consists of comparator A07U120 and a 3-volt Zener diode,
A07VR100.
Comparator A07U120 compares Vcc - 3 volts (2 volts at this point) at pin 3 with the threshold voltage at pin 2. If Vcc is
more than 4.6 volts A07U120 will output a low at pin 7. When Vcc is less than 4.6 volts, pin 3 is lower than the threshold
voltage, and A07U120 will output a at pin 7. When the output signal at pin 7 of comparator A07U120 is high, it indicates
that Vcc is low. If the output of A07U120 is not correct, adjust A07R101 using the adjustment procedure in Section 5.
Chip Select Controller. The chip select controller consists of A07U21C, A07Q120, and A07Q150, The Vcc LOW signal
is connected to the base of A07Q120. When system power starts to fail, the Vcc LOW signal changes to high and
A07Q120 turns OFF. Then, the input at pin 10 of A07U21 quickly changes to low. When the system power comes back
up, the Vcc LOW signal falls to low and A07Q120 turns ON. Then the input at pin 10 of A07U21 becomes high, and pin 11
of A07U21 slowly rises to high.
The output at pin 8 of A07U21 is connected to the base of A07Q150. When Vcc is LOW, A07Q150 is OFF and pin 18 of
A07U7 (chip select) stays high. When Vcc voltage is normal (not LOW) A07Q150 is controlled by the NVMCS (non-
volatile chip select) signal.
4-30
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 ...