ATG429EBPOperationManual
4‐1
June4,2015
Rev.A2
4 THEORY OF OPERATION
4.1 GENERAL CIRCUIT THEORY
The ATG Model 429EBP, P/N 01-1001-10, ARINC 429 single channel transmitter and receiver consists of
three board level sub-assemblies and a battery pack. The three boards are:
1. Display Board (P/N 20-6782-10)
2.
Digital Board (P/N 20-6784-40)
3.
Analog Board (P/N 20-6783-00)
4.1.1 DISPLAY BOARD
The Display board performs the human interface function for the 429EBP. It has three major sections of
circuitry:
1. Display circuits
2.
Keypad circuits
3.
Slide Switch circuits
The Display circuits output data in visual form. The display circuit consists of the liquid crystal display
(DS1). The Keypad switches allow data to be input to the unit. The keypad circuits consist of 23
momentary contact switches (S1 - S23). The switches are arranged in an X/Y matrix and are decoded by
the firmware on the digital board. The slide switches allow various I/O information (Parity, TX Baud, etc.)
to be changed and to turn the unit on and off. The slide switch circuits consist of 5 SPST slide switches
(S24 - S28) and various discrete components (resistors, transistors and capacitors).
4.1.2 DIGITAL BOARD
The Digital board contains the digital circuitry for the 429EBP. This circuitry has three major sections:
1. Control circuits
2.
429 Receive Buffer
3.
429 Generator
The Control circuits are the `Heart' of the system that controls and monitors all other circuits in the
system. The control circuits consist of the following components:
1. Microcontroller (U1)
2.
Firmware EPROM (U2)
3.
RAM (U3)
4.
Address Latch (U4)
5.
RAM IO (U5)
The control circuits monitor the number of `bits' received and upon completion, will read the receive
buffer.
The 429 Receive buffer stores the 429 bit stream data (Converted to TTL levels by the Analog board).
The following components make up the 429 receive buffer.
1. Bit Latch (1/2 U8)
2.
Serial Register (1/2 U6)
3.
Mux (U14)
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