Altair8800_Mister

By Fred VanEijk and Cyril Venditti.

What is an Altair 8800

https://en.wikipedia.org/wiki/Altair_8800

How to control the MiSTer Altair8800

• To move the cursor use the directional arrow keys (Left – Right – Up – Down).

• Toggle switches

  • SENSE/DATA/ADDRESS
  • OFF/ON
  • STOP/RUN
    • 1 key - On - up
    • 2 or 0 key - Off - down

• Momentary switches

  • SINGLE STEP
  • EXAMINE
  • DEPOSIT
  • RESET
    • 1 key - Up
    • 2 key - Down

• Not implemented switches

  • CLR
  • PROTECT
  • AUX

Available samples

These samples are accessible through the MiSTer Core OSD (F12) in the "Select Program" section.

• Empty

  256 bytes of zeroed memory at address 0x0000.
  

• zeroToseven

  256 bytes of memory with 1st 8 bytes as 0 to 7.
  First press the RESET toggle, then you can use the EXAMINE NEXT to step through 
  the data in memory.  You will see the values 0 to 7 as binary on the data LEDs.
  

• KillBits

  Kill the Bit game by Dean McDaniel, May 15, 1975
  Object: Kill the rotating bit. If you miss the lit bit, another bit turns on leaving two bits to destroy. 
  Quickly toggle the switch, don't leave the switch in the up position. 
  Before starting, make sure all the switches are in the down position.
  see: rtl\roms\altair\killbits.txt
  

• SIOEcho (See Serial port section)

  256 bytes to test serial port at port 00/01.
  Just echos the character typed on the terminal.
  see: rtl\roms\altair\SIOEcho.txt
  

• StatusLights

  Demonstrate status light combinations.
  Halts the cpu when done so requires a reset of the core.
  Single Step this one.
  see: rtl\roms\altair\StatusLights.txt
  

• Basic4k32 (see Serial port section)

  This is the basic interpreter originally created by Bill Gates and Paul Allen.
  Basic interpreter in 4k ram at 0x0000 with a total of 8k of memory including the interpreter.
  Communication with the serial port requires SENSE swithes to be set to 0xFD.
  
  The Basic4k32 requires the serial port to be setup to interact with it on a serial terminal.  
  The sense switches to be set as follows (note the sense switches are the switches below the upper 8 address LEDs).  
  
  Basic will not start properly unless the sense switches are set as follows:
  - 15 to 10 ON
  - 9 OFF
  - 8 ON
  The sense switches control some aspects of initializing the serial port on the Altair8800.
  

Altair operation

https://altairclone.com/altair_experience.htm

OSD explanation

MiSTer Core OSD (F12 or OSD button) :

• “Select Program”

  See Available samples section.
  

• “Load Program”

  Do this switch sequence to run a progrm:
  - Turn the ON/OFF switch to ON
  - Insure that the STOP/RUN switch is STOP
  - Load a program by using the "Select Program" option then press "Load Program".
        Once you press "Load Program" the Core will place that program in memory.
  Finally do:
  - RESET with the RESET/CLR switch
  - Turn the STOP/RUN switch to RUN alternatively use SINGLE STEP
  

• “Enable TurnMon"

  Makes available the turn key monitor at address 0xFD00.
  See file "rtl\roms\altair\turnmon.txt".
  

• “Serial Port"

  Console Port - use the MiSTer console port or SSH
  User IO Port - use the MiSTer user I/O USB 3.1 port
  

• “Reset”

  This will reset the core. Note this is not the same as RESET on the fron panel (which sets the program counter to 0).
  

• “Help”

  This will show this document on the Mister display.  Note this option is on the System OSD display.
  

Serial port

We have implemented a serial port as part of the Altair8800 core. To use it you need to have an I/O Board v5.5 or later with a USER I/O port. If you do not have this I/O board you can wire directly to the DE10-Nano.

Without the I/O board:

• Any USB to 3.3V (NOT 5.5V) TTL Serial Cable Adapter should work.
  • TX of the TTL Serial Cable Adapter -> SCL Arduino_IO15 pin of the DE-10.
  • RX of the TTL Serial Cable Adapter -> SDA Arduino_IO14 pin of the DE-10.
  • Don't forget to wire the Ground.

With the I/O board: The User Port (which looks like a USB 3.1A connector) is documented here: https://github.com/MiSTer-devel/Wiki_MiSTer/wiki/emu---Top-Level-of-a-MiSTer-core

• Any USB to 3.3V (NOT 5.5V) TTL Serial Cable Adapter should work.
  • TX of the TTL Serial Cable Adapter -> RX/SCL/D+ pin 3 of the User Port.
  • RX of the TTL Serial Cable Adapter -> TX/SDA/D- pin 2 of the User Port.
  • Don't forget to wire the Ground -> GND pin 4 of the User Port.

Use Putty or TeraTerm as a client and use the 19200 baud setting at 8 bits and no parity (this is required to run the Basic4k32 example).

This cable should work fine. https://a.co/d/dMlEKn4

with this USB 3.0 adapter https://a.co/d/1VpqE5a

For SSH with PuTTY

• Connect to the ip address of your MiSTer fpga.

Linux command line to establish the connection to the core

1. Identify the UART device:

   • Usually mapped to /dev/ttyS1 or /dev/ttyUSB0

   • Use this command to help identify the correct device:

     dmesg | grep tty

2. Access the serial terminal:

   • Use screen or minicom

   • Example command with screen:

     screen /dev/ttyS1 19200

   • Replace /dev/ttyS1 with the correct device identifier

   • Change 19200 to the appropriate baud rate if different

3. Enable Flow Control:

   • Use stty

     stty -F /dev/ttyS1 crtscts

   • Replace /dev/ttyS1 with the correct device identifier

   • This is done before the screen command

STEPS TO CONNECT CONSOLE PORT - direct serial mode

Assumes your MiSTer Console port is connected at COM4

reboot mister

connect to console com4 at 115200 with putty login un:root pw:1 load altair core

screen /dev/ttys1 19200

select basic4k32 in osd press load program in osd select console port in osd set sense switches on Altair front panel

• 15 to 10 on
• 9 off
• 8 on

select on switch select run switch

MEMORY SIZE? TERMINAL WIDTH? WANT SIN? Y

4823 BYTES FREE

BASIC VERSION 3.2 [4K VERSION]

Python Serial Terminal for Altair8800_MiSTer

A simple, lightweight serial terminal program written in Python specifically designed to work with the Altair8800_MiSTer core. Features include:

• Clean 80x25 character display with green text on black background
• Hardware serial connection at 19200 baud (8N1)
• True hardware echo handling (no local echo)
• Proper handling of CR+LF sequences for Altair compatibility
• Live TX/RX hex display for debugging
• Status line showing current port and connection settings
• ESC key to exit

Requirements

• Python 3.x
• pyserial library (pip install pyserial)
• tkinter (typically included with Python)

Usage

1. Connect your TTL Serial Cable Adapter to the MiSTer's User I/O port
2. Run the terminal program:
   • Default port (COM9): python term.py
   • Specify a different port: python term.py -p COM4
3. The terminal will connect at 19200 baud
4. Characters typed will be sent to the Altair and displayed when echoed back

Perfect for use with Altair BASIC and other software requiring serial terminal interaction.

Additional Information

For more details on console connection, refer to the official MiSTer documentation: MiSTer Console Connection Guide

Credits

• Inspiration for displaying the Altair8800 front panel: https://timetoexplore.net/blog/arty-fpga-vga-verilog-01

• Altair8800 front panel image: http://www.vintage-computer.com/altair8800.shtml

• Core: https://github.com/1801BM1/vm80a

  https://zeptobars.com/en/read/KR580VM80A-intel-i8080-verilog-reverse-engineering

  https://hackaday.com/2015/03/07/looking-inside-the-kr580vm80a-soviet-i8080-clone/

  https://jeelabs.org/2016/09/i-never-had-an-intel-8080/

  https://github.com/mmicko/s100fpga

Known issues

Depending on your monitor resolution the Altair8800 front panel might not be complete or centered.

Not implemented

The following switches/functions are not implemented:

• CLR
• PROTECT
• AUX