MOD8 MONITOR-8 Resident Monitor - Mil Mod 8/80

The MOD8 MONITOR-8 is the built-in resident monitor for the Mil Mod 8/80 system, residing in EPROM on the Mil8 64 memory board. This compact software provides essential tools for memory examination, modification, data loading/dumping, execution, block operations, breakpoints, and on-board EPROM programming — all via a simple terminal interface at 110 baud. Originally detailed in the Microsystems International Limited MF8008 Applications Manual, MONITOR-8 enables direct hands-on development on the early 8008-based hardware without external loaders or assemblers. In the MicroBasement, it showcases the minimalist yet powerful command-driven environment that defined early microcomputer prototyping.

Starting the Monitor

Configure Switch 1 on the Mil8 64 memory board with position 3 on and position 7 off to select the MONITOR-8 EPROM. No external boot loader is needed. Power on or press the Reset button on the Mil Mod 8/80 — execution begins immediately at octal location 000 000.

The first thing displayed on the terminal is the prompt '--------', indicating the monitor is ready to receive commands. No additional sign-on message appears. Use the standard terminal setup: 110 baud, 7 data bits, no parity, 1 stop bit via RS232 to current loop converter.

Command Entry Rules

Commands are exactly three letters, some followed by numeric operands in octal. Observe these strict rules for reliable operation:

• Characters typed are always echoed due to the bit-bashed UART — echoed input does not confirm command acceptance.
• Do not type SPACE characters in most commands; the monitor inserts needed spaces automatically, and extra spaces cause confusion.
• Do not press ENTER; the monitor detects command completion internally — extra ENTERs confuse it.
• All numbers are octal: bytes as three digits (bbb), words as six digits in split-octal format (wwwwww = two groups of three digits for high/low 8 bits each, e.g., all-1's 16-bit word is 377377).
• When expecting numeric input, non-numeric characters are ignored until valid digits arrive — this can make mistyped commands appear to hang.
• Some commands prompt on a new line with '*' while awaiting additional addresses or data.

Errors often produce no indication — incorrect action simply occurs. Enter commands exactly as shown, without spaces or ENTER unless specified in sub-commands.

Monitor Commands

Commands (enter exactly three letters, no spaces/ENTER unless noted):

• LOC wwwwww — Set Current LOCation Pointer (CLP) to word address wwwwww.
• DLP — Display current CLP (shows current location pointer).
• DPS — DumP Symbolic (disassemble memory).
  *wwwwww wwwwww — Starting and ending address.
• LDO — LoaD Octal data.
  *wwwwww wwwwww — Starting and ending address.
  / bbb bbb bbb ... — Data bytes ( '/' and SPACEs required here).
  More lines as needed...
• DPO — DumP Octal.
  *wwwwww wwwwww — Starting and ending address.
  Press any key after addresses to start dump.
• LBF — Load BNPF data.
  *wwwwww wwwwww — Starting and ending address.
  BxxxxxxxxF ... — BNPF data (x: N=0, P=1).
• DBF — Dump BNPF data.
  *wwwwww wwwwww — Starting and ending address.
  Press any key after addresses to start dump.
• EDT — EDiT memory at CLP.
  Sub-commands (prompts with wwwwww/):
  bbb — Enter byte value.
  (space) — Display current value and advance.
  ^ — Backup to previous location.
  R — Return to monitor prompt.
  @ wwwwww — Execute at wwwwww.
• XQT wwwwww — eXeQuTe program at address wwwwww.
• CPY — CoPY memory block.
  *wwwwww wwwwww — Source starting and ending address.
  *wwwwww — Destination address.
• TRN — TRaNslate code (relocate).
  *wwwwww wwwwww — Starting and ending address.
  bbb bbb — Original and new bank (256-byte page).
• SBP — Set BreakPoint.
  *wwwwww — Breakpoint address.
• CBP — Clear BreakPoint.
• PRG — PRoGram EPROM.
  *wwwwww wwwwww — Starting and ending address.
  %A or N — Select 1702A or 1702(N).

Legacy

The MOD8 MONITOR-8 captures the essence of early microcomputer software: a lean, EPROM-resident toolset that empowered users to build, debug, and program directly on minimal hardware. Preserving and demonstrating this monitor is vital because it represents the pioneering efforts of engineers and hobbyists who laid the pathways for modern computing. The command-driven interface, octal-based entry, bit-bashed I/O handling, and integrated EPROM programmer exemplified the hands-on, low-level control that evolved into today's IDEs, debuggers, flash programmers, and embedded development environments. By keeping MONITOR-8 operational on real Mil Mod 8/80 hardware in the MicroBasement, these foundational innovations remain tangible and inspiring, honoring the ingenuity that sparked the personal computing era and continues to influence open hardware and retro computing communities today.

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