DEC-10 RSCB-D PDP-8 Scanner For PDP-10 196803

This document describes SCN680 (or SCN689), a PDP-8 software program designed to function as a character scanner for a PDP-10 system. It performs the same role as dedicated hardware scanners (like the 630 DCS or DC10), handling 8-bit character assembly for multiple Teletype lines.

Key aspects include:

• Functionality: SCN680 processes characters from Teletype lines connected to the 680 Data Communication System Hardware and transmits them to the PDP-10. It includes modified 8-bit character assembly subroutines.
• System Requirements: It necessitates a minimum configuration PDP-8, the 680 Data Communication System Hardware, a DA10 PDP-10 to PDP-8 interface, and a PDP-10 running a time-sharing monitor properly interfaced with the DA10/SCN680 package.
• PDP-8 Operation: The program is loaded from paper tape (BIN format). Once loaded and started at address 200g, it can run indefinitely, even if the PDP-10 monitor is stopped and restarted. The number of Teletype lines it manages is configured by setting a value (representing the highest physical line number) in PDP-8 memory location 377; the program dynamically adjusts its line-number dependent components upon restart, eliminating the need for a full reload if line configurations change.
• PDP-10 Interface: The PDP-10 interacts with SCN680 by initializing it (clearing buffer flags and assigning a Program Interrupt channel). The PDP-10 receives interrupts signaling two conditions: when its receive buffer (To-10-Buffer) is full (data is available from a Teletype) or when its transmit buffer (From-10-Buffer) is empty (ready to accept data for a Teletype). Data is transmitted and received using specific instructions (DATAO and DATAI) with a defined format that includes both the line number and the character.
• Assembly: SCN680 can be assembled for different clock speeds (Clock 1-4) on the 680 hardware by specifying the desired clock number during the assembly process.