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TM 11-6625-3145-14
Theory of Operation-318/338 Service
External Trigger Latch and Data Polarity. Latched data D3 of A07U31 is applied to pin 10 of A07U1 2C. This signal is
used to select the external trigger polarity. If the polarity is positive, the external trigger’s positive-going edge sets
A07U22B. If polarity is negative, the external trigger’s negative-going edge sets A07U22B. A negative-going edge from
pin 14 of the I/O selector A07U30 resets A07U22B.
The MPU can read the status of A07U22B at pin 3 (DO) of tri-state output buffer A07U32. The out- put signal at pin 15 of
I/O selector A07U30 controls the enable line of A07U32.
Latched data D2 from A07U31 is applied to pin 1 of A07U12A. This signal is used to select input data polarity.
Serial I/O Controller. The serial Input/Output controller (SIO, device A07U2) handles serial-to-parallel interfacing.
When receiving data, the SIO checks for stop bits, parity, sync characters, framing errors, and overrun errors. When
transmitting data, the SIO handles such tasks as sync character insertion, adding parity bits, and adding stop bits.
The Z-80A CPU supplies the CPU clock signal to SIO pin 20 as the control clock (3.68 MHz). A07U12B and U32B adjust
the clock waveform before it reaches the SIO.
When the SIO generates an interrupt, it generates a low signal at pin 5 that ties to the bus INT line.
The SIO contains two serial data tranceivers: PORT-A receives data on pin #12 and a clock on pin 13, PORT-B receives
data on pin 28 and a clock on pin 27. PORT-A is used for serial data acquisition and PORT-B is used for RS-232 control.
The SIO contains two signal sets for modem control, but only one set is used for RS-232 modem control. The RS-232
modem control input signals (pins 22 and 23) and input data spin 28) are tied to the RS-232 receiver, A07U40. The
RS-232 modem control output signals (pins 24 and 25), and out-put data (pin 26) are tied to the RS-232 transmitter,
A07U41.
In this system, the SIO is mapped by I/O address. Assigned SIO addresses are 90 and 91 for PORT-A, and 92 and 93 for
PORT-B. The output at pin 11 of I/O selector A07U30 is tied to pin 35 of the SOG. Bus AB1 is tied to SIO pin 34, and bus
ABO is tied to pin 33. These three inputs control SIO addressing.
Table 4-9.
OPTION I/O DEVICE ADDRESSING AND FUNCTION
AB4
AB3
AB2
Address
Function
L
L
L
80 - 83
Read status (external trigger, battery voltage, modem DSR).
L
L
H
84 - 87
Reset external trigger latch.
L
H
L
88 - 8B
Set RS-232 bit rate generator.
L
H
H
8C - 8F
Set SERIAL bit rate generator, data polarity, external trigger
polarity.
H
L
L
90 - 93
Select SIO.
H
L
H
94 - 97
Not used.
H
H
L
98 - 9B
Not used.
H
H
H
9C - 9F
Not used.
4-33
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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