PDP-7 Interface And

This manual details the interface characteristics and installation planning for the Programmed Data Processor-7 (PDP-7) computer, specifically for systems with serial numbers above 100. The PDP-7 is an 18-bit general-purpose binary computer with a 1.75 µsec core memory cycle time, featuring flexible I/O capabilities for connecting over 64 peripheral devices. It describes two primary data transfer methods: programmed data transfers and data break transfers, along with the underlying digital logic circuits and physical installation requirements.

Programmed data transfers, controlled by the computer program, utilize the Accumulator (AC), Information Distributor (ID) for output, and Information Collector (IC) for input. The system incorporates an Input/Output Skip (IOS) facility for conditional program branching and a Program Interrupt (PI) facility for real-time device servicing. Input/Output Transfer (IOT) instructions, generated by the IOP Generator and Device Selector (DS), command these transfers and device operations, operating in normal (1.75 µsec) or slow (adjustable 1-4 µsec) timing cycles.

Data break transfers allow external devices to directly access the PDP-7's core memory via a cycle-stealing mechanism, bypassing program control for high-speed block data transfers (over 10 million bits/sec). This involves signals such as DATA BREAK REQUEST, TRANSFER DIRECTION, DATA ADDRESS, and DATA INFORMATION, managed by the Data Break Facility to ensure synchronized memory access.

The document also describes the standard Digital Equipment Corporation (DEC) FLIP CHIP logic circuits—including inverters, bus drivers, pulse amplifiers, and diode gates—used in the PDP-7 interface. It provides detailed information on interface connections, signal identification, loading and driving considerations for external devices, and comprehensive planning for system installation, covering physical configuration, environmental requirements (temperature, humidity), power (115V, 60-cps), and cabling. An appendix lists the Device Selector and Information Collector channel requirements for various standard PDP-7 options, aiding in system expansion.