DECsystem-10 and DECsystem-20 KL System Reference Card

This document is a KL System Reference Card for DECsystem-10 and DECSYSTEM-20, serving as a comprehensive quick reference guide for various aspects of the system's architecture and programming.

Key information included:

1. ASCII Character Set: A table showing octal, decimal, and SIXBIT representations of characters, along with notes on SIXBIT's compression use, teleprinter codes, ASCII parity, and international variations.
2. Input-Output Instructions: A list of mnemonic codes for various I/O operations (e.g., BLKI, DATAI, RDCSB, WRFIL).
3. Instruction Codes: A large table (partially unreadable in OCR) outlining the machine instruction set, including details on operand types, flags, and instruction categories (MOV, ADD, AND, SKIP, HALT, etc.).
4. Process Table Configurations (TOPS-10 and TOPS-20): Detailed memory layouts (addressed from UBR/EBR) showing the organization of system areas, including:
   • Eight-channel logout areas
   • Standard priority interrupt instructions
   • Four-channel block fill words
   • DTE20 control blocks
   • Executive arithmetic overflow/stack overflow/trap instructions
   • Page fail words, flags, old/new PC words
   • Time base, user process execution time, user memory reference count
   • Pointers for executive and user sections.
5. Instruction Formats:
   • Basic, KL10 In-Out, and Extended instruction formats, detailing bit fields for instruction code, device code, index registers, and operands.
   • Local/Global Indirect Word and Index Register formats.
6. CPU State and Memory Addressing:
   • PC Word: Program Counter status flags (carry, overflow, public, trap, divide, etc.).
   • Flag-PC Double Word: Combined flags and PC information.
   • Stack Pointers: Local and Global Stack Pointer formats, including control count and in-section of last item.
   • Byte Pointers: One-word and Two-word Byte Pointer formats for flexible memory access.
   • Floating Point Operands: Formats for single and multiple length fixed-point and floating-point numbers.
7. Input/Output and Interrupt Control:
   • CONO PI/APR: Conditions Out instructions for Priority Interrupt and Processor Flags, showing bit fields for write parity, selected interrupt levels, system turn on/off, and program request handling.
   • CONI PI/APR: Conditions In instructions for Priority Interrupt and Processor Flags, showing program requests on levels and interrupt in progress status.
   • API Word Format: Details for Address Space, Function, and Qualifier bits used in I/O operations.
8. TOPS-20 Specific Memory Mapping:
   • Page Map Entry, Sector Pointer, Map Pointer, and CST Entry formats, detailing fields for type, public/writable status, cache control, and physical/virtual page numbers.
9. System Diagnostics/Microcode:
   • Microcode Version Word and Microcode Fault Status Word formats, providing information on the microcode state and errors.