4709 Sep65

The Digital Equipment Corporation (DEC) 4709 7 Bit Transmitter (dated 9/8/65) is a parallel-to-serial converter designed to transfer 7-bit digital information from a parallel device to an outgoing serial asynchronous data line. It is self-contained on a double-length DEC System Module board.

Key Features and Operation:

• Function: Disassembles a 7-bit parallel data character in a shift register, adds a Start bit and a Stop element, and transmits it serially. The least significant bit follows the Start bit.
• Configurable Stop Element: The duration of the Stop element can be set via jumpers to 1.0, 1.5, or 2.0 units of time. This results in total character lengths (including Start, 7 data bits, and Stop) of 9.0, 9.5, or 10.0 units respectively.
• Transmission Flow: An external device loads a 7-bit character. The module enters an "Active" state for transmission, sending the Start bit, followed by the 7 data bits at one-unit intervals. Upon completion, it enters an "Inactive" state, sends the Stop element, and activates a "Flag."
• Flag Output: The "Flag" indicates to the external device that a character has been transmitted and the next character can be loaded. An indicator light on the module handle provides visual feedback of the Flag state.
• "Wait" Input: A "Wait" input can prevent the Stop Element Counter from timing out, useful for half-duplex operations.
• Clock Input: Requires a clock frequency of twice the desired baud or bit rate, with a maximum input of 25 kHz, supporting baud rates up to 12.5 kHz.
• Flexibility: Designed for various interfaces, including computer systems and displays, with flexible data output signals (including complementary outputs).
• Power-Up Recommendation: It is recommended to transmit a character of "all ones" as the first character after power is restored to ensure correct initial operation.

Technical Specifications:

• Inputs: Utilizes DEC Standard Levels or 0.4 microsecond negative pulses for various control and data inputs (Clock, Read In, Data Bits 1-7, Enable, Clear Flag, Wait).
• Outputs: Provides DEC Standard Level data outputs, a high-current data output (up to 100 mA from negative voltages), and an "Active" status output.
• Power Requirements: -15 volts at 225 mA and +10 volts at 9 mA.