4702 Jun65

The DEC 4702 5-BIT TELETYPE RECEIVER (dated 6/14/65, priced $200.00) is a self-contained serial-to-parallel converter designed for asynchronous teletype lines and similar serial data applications. Housed on a double-length DEC System Module board, it converts incoming serial 5-bit characters (which include Start and Stop elements, totaling 7.0, 7.5, or 8.0 units) into a parallel digital format.

Operational Overview: The receiver actively monitors the input line. Upon recognizing a Start element, it synchronizes, becomes active, and resets its internal shift register. It then samples the incoming bit stream at half-unit and full-unit intervals to validate the Start bit and then capture the 5 data bits. Once the complete character is assembled, a "Flag" output is set (indicated by an integrated lamp), signaling an external device that the parallel data is ready for transfer. The Flag can then be cleared after the data is read. The unit then enters an inactive state, waiting for the next Start pulse.

Key Features & Specifications:

• Character Format: Processes 5-bit characters, removing the Start and Stop elements. Supports configurable Stop bit lengths (1, 1.5, or 2 units) via internal jumpers.
• Clock Input: Requires a clock signal 8 times the baud rate, with a maximum frequency of 100 KHz (supporting baud rates up to 12.5 KHz).
• Data Input: Interprets a Mark state as ground and a Space state as -3V.
• Outputs: Provides parallel outputs for the 5-bit character, additional bits (6-8) with jumper-selectable logic levels, an "Active" signal indicating receiver operation, and the "Flag" output for data readiness.
• Configurability: Internal jumpers allow customization of Stop element length, specific output bit logic levels, and Flag clearing behavior.
• Power Requirements: Operates on -15V at 150mA and +10V at 5mA.
• Timing: Formulas are provided to calculate the maximum permissible time to sample the data after the Flag has been set.