Theory of Operation
TDS 340A, TDS 360 & TDS 380 Technical Reference
3–13
A2/A3 Option 14 Board
The A2 Option Board has GPIB, RS-232, and Centronics interfaces for external
control and hard copy operations. The A3 board has VGA Video output and
printer power interfaces.
Refer to schematic A2
. Signals travel from the processor board through the
J1 connector to the U2 address decoder. U2 uses lines A15, A16, and A18 to
break incoming addresses to either the RS-232, Centronics, GPIB or option
ROM.
The GPIB circuitry is composed of GPIB controller U8, with transceivers U9
and U10 buffering signals to and from the GPIB on the option board.
Refer to schematic A2
. The RS-232 portion of the board connects to the rear
panel through port J2. Signals travel from the processor board through the J1
connector to the U4 dual asynchronous receiver/transmitter (DUART). The
DUART sends data to the U5 driver/receiver. U5 converts signals from logic
levels on the DUART side to RS-232 levels at the 9-pin connector. From U5,
information goes out port P2.
The Centronics portion of the board connects to the rear panel through the 9-pin
connector J3. Data travels from the processor board through the J1 connector to
register U6 where it is sent out J3. U4 manages control signals. U12 buffers
printer status information to be read through U4.
Refer to schematic A3
. The 9-pin VGA video connector routes auxiliary
HSYNC, VSYNC, and VIDEO signals from main board connector J703 to the
rear panel.
The printer power converter uses switching regulator U1 to convert +15 V from
the power supply to +8 V output at rear panel connector J2. This provides power
for the Option 3P thermal printer.
A6 Front Panel
The CPU system sends instructions to and receives information from the
Front-Panel Processor on the Front-Panel Board. The Front-Panel Processor
reads the front-panel switches and ports, and reports any change in their settings
to the processor system. The Front-Panel Processor also turns the LEDs on
and off.
The Front-Panel Processor reads the front-panel menu switches and sends any
changes in menu selections to the CPU system. The Front Panel Processor does
not read the ON/STBY button; its signal passes through the Front-Panel Board
and the Main Board to the A20 Low Voltage Power Supply.
The front panel also generates the probe compensation signal.
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