TM 11-5821-333-30
CHAPTER 3
MAINTENANCE INSTRUCTIONS FOR RADIO SET CONTROL
C-11466/ARC-201(V) AND C-11466A/ARC-201A(V)
Section I. PRINCIPLES OF OPERATION
3-1. INTRODUCTION
The control unit has three electronic modules, a control paneI, and a chassis. Figure 3-1 is a functional block
diagram.
The control panel (A1) includes the control switches, volume control, data entry keyboard, and display.
The electronic modules are
l Circuit Card Assembly, Bus Interface (A2)
l Circuit Card Assembly, Processor (A3)
l Electronic Components Assembly, Power Supply (A4)
The chassis (A5) includes the backplane assembly (parent board) and the chassis side rails.
All inputs and outputs pass through J1 on the power supply. Many signals pass through unchanged. The power
supply converts +28 V dc into +5 V dc for digital circuits and -22 V dc for the display. A grounded TAKE CONTROL
input disables the control unit. A circuit on the power supply bypasses the volume control when TAKE CONTROL
is grounded.
The control unit is processor controlled. The processor has a microprocessor, memory, and DMA control cir-
cuits. These command the operation of the rest of the control unit and store data for later transfer to display or rt.
DATA DIRECTION output determines direction of data transfer between control unit and rt. Display data is trans-
ferred to the front panel over a serial data line. Switch status signals are received from the front panel over an
eight-bit parallel data bus.
The bus interface consists of buffers and timing circuits used between rt and processor. Some functions are
l energizes front panel switches for reading by processor,
l reads keyboard switch closures, decodes, and sends to processor,
l converts parallel data from processor to serial data and sends data to rt over differential DATA (+) and
DATA (-) lines,
l supplies differential CLOCK (+) and CLOCK (–) signal to transfer data to rt,
l supplies clock to display,
l receives differential data from rt on DATA (+) and DATA (–) and sends to processor,
l resets processor on power-up, whenever TAKE CONTROL switch changes position, or for low voltage
condition on 28 V dc input.
The 115 V ac input is used to illuminate the front panel, The T-ZERO-N output is from the Z-A position of the
FUNCTION switch. POWER ON/OFF is also from the FUNCTION switch and supplies +28 V dc to the rt in all posi-
tions except STOW.
3-1
