Briel Computers Altair 8800 micro User manual

Altair 8800micro
Setup and Users Manual
Setup and Users ManualSetup and Users Manual
Setup and Users Manual
JULY 2010 PRELIMINARY MANUAL
Briel Computers
Briel ComputersBriel Computers
Briel Computers
5392 Cornell Blvd
North Ridgeville, OH 44039

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All materials, schematics, and hardware designs provided without any warranties. Although this material has been carefully examined,
Briel Computers takes no responsibility for any errors in printing.
Version 1.0
Published by Briel Computers
5392 Cornell Blvd
North Ridgeville, OH 44039
USA
Copyright 2010 Briel Computers; All rights reserved. Printed in the United States of America. Except as permitted under the
Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a
database or retrieval system, without the prior written permission of the publisher, with the exception that the program listings may be
entered, stored, and executed in a computer system, but they may not be reproduced for publication.

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Forward
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Recreating a cult classic
Anybody who has been even remotely involved in vintage computers knows of the Altair 8800. There have
been many discussions on the first personal computer, the first home computer, but nobody can argue that the
Altair set the industry in motion.
Original Altair 8800 system
The original Altair 8800 was designed in 1975 by Ed Roberts founder of MITS (Micro Instrumentation and
Telemetry Systems).
Ed Roberts shown next to some of his Altair machines

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In 1977, Ed Roberts moved back to rural Georgia after the sale of MITS to Pertec. Nearby Mercer University
started a medical school in 1982 and Ed Roberts went on to be the first graduating class and get his medical
degree in 1986. He did his residency in internal medicine and in 1988 established his own practice. Ed Roberts
died on April 1, 2010 after a long bout of pneumonia at the age of 68. The computer system he created was
introduced to the world in the January 1975 edition of Popular Electronics and shall live on forever.
January 1975 Popular Electronics featuring the ALTAIR 8800
The article describes the entire system of the Altair and took two issues to cover the entire system. The
production version was not ready at the time and MITS had this case made for the magazine article. You could
purchase an affordable base kit for $439 which included the case, CPU board and 256 bytes of memory. The
assembled version was $621. Soon after the release Bill Gates sent Ed Roberts a letter stating he had a software
company that had BASIC that would work on the Altair. Paul Allen came to MITS in Albuquerque to
demonstrate their program using paper tape; it crashed after it displayed “Altair Basic”. The next day a new
paper tape reader was brought in and BASIC loaded successfully. This was the beginning of Microsoft, the
largest software company in history.
Copies of BASIC were bundled with a pair of Altair 4K RAM boards for $75. However, the RAM boards were
flawed and most users did not want those boards. Robert Marsh who formed Processor Technology offered 4K
static RAM boards for $255. His company was the most successful company that produced Altair compatible
products. This kept many hobbyists from wanting the flawed 4K MITS boards and the full retail price for
BASIC from Micro-Soft was $500. The Homebrew computer club was formed in 1975 and the primary
computer there was the Altair 8800 system. Steve Dompier passed a copy of the pre-release version of BASIC
to Dan Sokol who had access to a high speed tape punch. The next day at the Homebrew Computer Club
meeting, 50 copies of BASIC were made available to members for $.50 each. Shortly, many people had copies
of BASIC and were passing it along freely. Word of this got back to Bill Gates and prompted this open letter to
hobbyists in 1976:

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The second letter was sent out to all major computer publications after a very strong negative response from
many in the field.
In late 1975 Imsai released the 8080 as a direct competing clone of the Altair. Most feel that the Imsai was a
better machine than the Altair and used the same bus expansion scheme. It wasn’t long before several other
companies also had clones using the S100 bus system. This led to several aftermarket companies developing
hardware add-on cards for the S100 bus systems.
By 1977 MITS had reached $6 million in sales when they were sold to Pertec. The company was soon merged
into the larger company (Pertec) and the name abandoned. The S100 bus system computers continued to be sold
well into the mid 80’s and I remember as late as 1990 still seeing ads for S100 boards in magazines.
The Altair 8800 is an icon for the start of the home computing industry. Long live the blinking lights :.::.:
Vince Briel

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Setup and Users Manual
Index
Chapter 1: Introducing the Altair 8800 micro 9
Chapter 2: Unpacking your system 13
Chapter 3: Building your kit with step by step instructions 15
Chapter 4: Powering up and testing your system 23
Chapter 5: Programming with the front panel 27
Chapter 6: Loading BASIC 29
Chapter 7: Saving memory to an SD card 30
Chapter 8: Loading a text file BASIC program listing 31
Chapter 9: On screen graphics and color 32
Chapter 10: Special front panel functions 33
Chapter 11: Performing a firmware update 35
Appendix A: Troubleshooting 36
Appendix B: The expansion port 37
Appendix C: Bill of materials 38
Appendix D: VT100 Control Commands 39

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Chapter 1: Introducing the Altair 8800 micro
The Altair 8800 micro is the result of 5 years of concept ideas and many failures. While the project spent much
time on the shelf, the desired result would keep this project alive. The micro is based on a simple early version
Altair 8800 with memory and a serial card for I/O. The project goal was to design a system that could be
programmed like the original with toggle switches and could run the original Altair BASIC programming
language. The micro is the first in a series of Altair clones that will be released. A full size version will be in the
works after the initial release of the micro that will be a front panel only and then the original concept AltairPC.
Final Altair 8800 micro prototype
You may have noticed that not all of the original Altair I/O status LED’s are on the front panel. This is due to
the limited amount of I/O and the limited amount of physical space allotted on the front panel itself. The
missing LED’s are INTE, PROT, WAIT, and HLDA. In addition to the missing LED’s one AUX switch was
also not included on the board. The AUX switches were not directly used on the original Altair but the one
AUX switch on the Altair micro serves as a boot loader and memory storage detector.
Choosing a processor was no easy choice. Most replica computers created by Briel Computers use authentic
processors that are identical to those used in the original systems. The Altair 8800 micro is different. The
original processor (i8080) has multiple voltage requirements making design implementation difficult for kit
purposes at a low price. The Z80 processor is very close to the 8080 and most code works with it. The problem
is that it doesn’t run Altair BASIC and was one of the failed concepts. This processor failure set the project
back over 2 years. After considering using the 8085 (software compatible), I opted to emulate the CPU in a
microcontroller. The main reason was chip reduction. With a microcontroller I am able to not only embed an
emulated version of the 8080; I can also emulate most of the Altair system in 1 chip. The main CPU
microcontroller has the nickname AOAC (Altair on a chip). While there are I/O pin limitations, a handful of
latches can give you as much I/O as you need.

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Writing an emulator for a CPU is a very difficult process if you’ve never written an emulator and you have very
little programming experience on the CPU you are emulating. My first step was to learn about a CPU that I
hadn’t used in 20 years. Many CPU’s share similar features such as accessing memory, having registers to work
with, math functions, ability to call routines, jump to memory locations, etc. It wasn’t long before I had a good
handle on the CPU and how it functioned. The hardware is a simple design. Using the Atmel AVR family
microcontroller was a simple choice. It is RISC based and many of the instructions only require one clock cycle
to perform. The heart of the code simply reads a memory location OP instruction and handles that instruction
exactly like the 8080 would. Some instructions were almost directly compatible to the Atmel instruction set
making emulation easy. Other instructions were much more difficult and required more code to interpret the
command.
Single step introduced a whole other problem. Not only does the microcontroller emulate the instruction, it
breaks it down into steps. As the original Altair single-steps through code, it does so one section of the
instruction at a time. For example, a jump to another address command first gets the opcode, and then on the
next step it fetches the low order byte of the address it is going to jump to. On the final step, it grabs the high
order byte. The next step will place the CPU at the new address.
With the core of the CPU and front panel emulation complete, the built on terminal section received its features.
The terminal section is from the Briel Computers PockeTerm with a lot of changes. The addition of an SD card
slot gives the ability to load and store programs and memory.
SD card slot on Altair 8800 micro
The SD card has the following features and conditions:
•Cards work with FAT16 or FAT32 only, no NTSF
•8.3 filename format, no using long names
•Root directory access only, no reading/writing to subdirectories
•Micro-SD cards can be used with an adapter
•Cards must not be removed while the system is on
The purpose of the SD card is to store and load BASIC, complete memory including BASIC and firmware
updates. The card was not designed to load disk operating systems and other such means of storage.
Modifications may be possible to do this in the future but not at this time.

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Altair 8800 micro VGA port
The VGA output port is part of the terminal system. Consider all of the I/O ports as part of the terminal
system and you will better understand how everything is connected. The VGA port gives the user an
800X600 display of 80X40 characters with a single color choice that can be modified on the keyboard. The
cursor can also be changed from a blinking square to solid or underscore, blinking or not, or no cursor at all
if you choose. Most monitors work just fine with this system, but it is software driven and not a hardware
VGA driver so some monitors may have more difficulty syncing up with the system. We have found this to
be a very rare occasion and you should have no issues with your monitor as long as it meets the system
specs. When using the VGA monitor in BASIC, you may want to do some cursor controls such as, turn off
the cursor and move the text location to X,Y. You can do these features using what is called VT100
commands. The VT100 commands are essentially code commands that tell the terminal section to perform a
specific function. One example that is commonly used is the HOME CURSOR command:
ESC[H
To use this command in basic the code would look like this:
10 PRINT CHR$(27)+”[H”;
This moves the cursor from wherever it was to the upper-left corner of the screen. Even if the cursor is off,
the next character to be displayed on the screen starts printing there. Other functions can be found in the
appendix section.
Composite video connector
Since the other video output choice is composite monitor, you can choose to use both setups at the same
time if you wish with no issues. The composite video output port is a full color 40X25 NTSC output port
capable of displaying full color characters with text block style graphics. You can turn on/off the cursor
using VT100 codes as well as clear the screen, home the cursor and set X,Y location of cursor. Not all
VT100 codes are capable with the composite output due to the smaller screen size and driver limitations.

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PS/2 keyboard port
The ps/2 keyboard port gives the user the ability to use a standard PC style keyboard to type data into the
system. The ps/2 port is also connected to the terminal section and any data from it is treated the same as a
standard terminal.
DC Power input jack
The power input connector is a 2.5mm connector that accepts DC positive center connector. We suggest
using a 1A (1000mA) 7-9V DC regulated power supply. If you connect the system with an incorrect power
supply that has the + on the external connection, there is circuit protection up to 1A.
The overall experience of the Altair 8800 mini will give the user a real life feel to what it was like to
program a computer with lights and switches in the pioneering days of computers. Kit builders will find the
experience of building a full system fun and rewarding.

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Chapter 2: Unpacking Your System
Ok, you’ve just received your Altair 8800 micro system, what do you do next? Well, if you purchased the kit,
you will want to skip ahead to chapter 3 on building your kit. If you have the assembled system, we can guide
you to getting it set up.
What you need for your Altair 8800 micro:
You can use a VGA monitor or TV with composite input.
Use a keyboard that has the ps/2 connector on it. A USB converter may not work properly.
The power supply needs to be at least 1000mA (1A) 7-9V DC positive center with a 2.1mm connector.
You will need an SD card or you can use a Micro SD card with the adapter to SD.

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Prepare a space for your Altair 8800 micro:
Make sure you have enough space to securely place a monitor behind your Altair. You can choose a CRT or
LCD style monitor. If you find you need to place something under the monitor to raise it above the Altair, use
caution that the monitor is stable and can not fall over. A good place for the keyboard is directly in front of the
Altair or alongside the unit. Before you go any further, make sure the switch is up (off) on the on/off switch on
the front panel.
Connecting up a monitor:
Using a monitor is optional, and you may wish to simply program the Altair from the front panel alone. In
which case, you don’t need a monitor connected. However, if you wish to run BASIC or another program
requiring text output, you need to connect to a monitor. You have 2 choices to choose from on the Altair micro.
You can choose a VGA monitor which gives you a nice crisp bold 80X40 text display of a single color choice,
or you can choose a composite monitor or TV to get full multi-color text and low-res text graphics. If you can’t
make up your mind, that’s ok, you can use both, and at the same time! My setup has a VGA monitor behind my
Altair micro and a small 7” LCD TV that sits right on top of my Altair. Please use caution if you place anything
on top of the Altair that it might not properly support the weight of your object.
Plug in your keyboard:
If you choose to use a keyboard for I/O, connect it to the PS/2 keyboard port in the rear of the Altair 8800
micro. Set it directly in front of the Altair with enough room to still be able to flip your switches.
Plug in an SD card:
If you are going to use an SD card to load/store programs, you must do this with the power turned OFF.
WARNING: Removing or installing the card while the power is on could result in damage to the card or
data loss. You may also use the newer micro-SD card but you will need to use an adapter for it to fit.
Add some power:
Using your own supplied power supply, plug the connector into the DC power connector port and plug the other
end to a wall socket. Make sure your power supply is 7-9V DC 1000mA (1A) power supply with positive center
supply.
WARNING: If you attempt to use an incorrect power supply, you could damage the Altair 8800 micro.
Please feel free to ask if you are unsure about your power supply or have any problems.
You are now ready to use your Altair 8800 micro and begin your new adventure in old school computing.

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Chapter 3: Building Your Kit with Step By Step Instructions
If you purchased your Altair 8800 micro as a kit, you will need to assemble it before you can begin
programming. In order to assemble your kit, you will be required to solder the components onto the 2 printed
circuit boards and mount the boards and panels in the case. We will demonstrate how to assemble the kit step by
step. You are encouraged to follow these steps as we have studied the best possible method for assembly with
the highest degree of success.
Inventory your parts for the mainboard from the following list:
PART QTY
ATMEGA 8515 CPU 1
62256 CYPRESS SRAM 1
74HCT573 LATCH 8
PROPELLER CHIP 1
EEPROM 1
5MHz CRYSTAL 1
16MHz CRYSTAL 1
LM7805 VOLTAGE REGULATOR 1
LM3940 VOLTAGE REGULATOR 1
40 PIN SOCKET 2
28 PIN SOCKET 1
20 PIN SOCKET 8
8 PIN SOCKET 1
100 OHM RESISTOR 2
220 OHM RESISTOR 6
470 OHM RESISTOR 3
560 OHM RESISTOR 1
1K OHM RESISTOR 1
3.3K OHM RESISTORS 5
.1uF CAPS 12
22pF CAPS 2
10uF CAPS 2
100uF CAP 1
1N4001 DIODE 1
PS/2 KEYBOARD CONNECTOR 1
RCA YELLOW VIDEO CONNECTOR 1
VGA CONNECTOR 1
HEADER CONNECTORS 3
SD CARD CONNECTOR 1
DC POWER CONNECTOR 1
SCREWS 6
NUTS 2
BLANK MAINBOARD PCB 1

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Tools required for assembly:
1. Soldering iron or gun (25-35W preferred)
2. Solder (low temp solder works best)
3. Phillips screwdriver
4. Wire cutters
5. Old dry towel for cleaning iron
Before you begin, make sure you have plenty of space to work with and have your components sorted into
sections. The front panel and mainboard sections come bagged separately to help avoid confusion and to locate
your parts quicker.
Plug your soldering iron or gun in and allow the iron to get hot. Make sure nothing is around the tip that can get
melted. Allow 5-10 minutes for your iron to fully heat up. Using a dry towel, wipe the tip clean of any old
solder. If you are using a gun, you need to hold the trigger to heat up most units. I will refer to your soldering
device as an iron from this point on.
Tin your iron by melting a small amount of solder directly onto the tip of your iron. If your iron is hot enough
the solder should melt with ease. Now, using your dry towel, wipe off the excess solder so that your tip looks
solder shiny but with only a very thin coat on the tip. This helps transfer the heat to the contact area for a better
solder flow.
You are now ready to assemble the mainboard using the following steps:
Step 1: Install the SD card slot. The SD card slot sits on the top of the PCB and there are 2 notches
that should fit into holes so that it is perfectly sitting on the board. Carefully solder all of the pins to their pads.
NOTE: Solder the 2 upper ground pads at each side of the SD card slot to the PCB
Step 2: Install the resistors. Resistors are small cylinder shaped components with wire sticking
out on each side. The colored bands identify the size of the resistor. Each resistor will have either a gold or
silver band. Hold the resistor so the gold or silver band is on the right side. Now look at the first colored band
on the left side. That color is the first digit of the resistor. Let’s assume your resistor has the color band pattern
Yellow, Violet, Red, and Gold. Looking at the chart on the next page you can calculate the value of that
resistor.

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Resistor color chart
The first color on the left is Yellow which equals the value 4. The 2nd color is Violet which equals 7. The 3rd
color is red. This is your multiplier. Red equals 2 so we add 2 zero’s to the end. So, the resistor value is 4-7-00
4700 or 4.7K. The gold band indicates that value will be within 5% of the value when measured.
Find the 3.3K resistor. The 3.3K resistor has the value Orange, Orange, Red, and Gold. Bend the metal wire
tabs at a 90 degree angle at the ceramic edges so the resistor forms a U shape. On the top side of your printed
circuit board (PCB) locate a resistor spot for 3.3K and insert the resistor into the holes and make the resistor sit
flat on the PCB. There is no polarity on the resistor so it does not matter which side gets inserted into which
hole. While holding the resistor flat on the board with one hand, turn over the board and open up the wires so
they point away from each other enough so that the resistor will not fall out. Set the board down on the table
and place your iron tip on one side of the round ring hole and on the wire. Count to 5 then touch the other side
of the hole with solder. Try not to touch the iron. Wait until the solder begins to melt and flow. Make sure you
are only touching the ring and the resistor wire with the iron. Apply enough solder so the wire forms the shape
of a triangle. At this point, remove the solder, then the iron. Check your work to make sure the solder adhered to
the ring only. Now solder the other resistor wire and ring. Cut the extra lead wire off close to the PCB. Repeat
with all the other resistors. I like to keep all my resistors facing the same way so that all the gold rings are on
the same side. It does not make any difference if you do this or not, but try not to unsolder a component unless
you have to. Please note that there is no resistor #15. R15 was removed from the design.
Step 3: Install the Crystals The Crystals are like the heartbeat of a CPU. CPU’s operate on
timing and synchronization. There is one 5MHz for the Propeller CPU (terminal) and one 16MHz crystal for the
ATMEGA8515 CPU (replaces 20MHz). The numbers are clearly labeled on top and they can be installed in
either direction. Like the resistor, install the wire leads until the component sits flush with the board. Hold the
component, turn over the board and separate the 2 leads away from one another to help hold the crystal on the
board. Now set the board down and solder the crystals to the board. Cut the extra lead length off.

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Step 4: Install the Diode. The diode is like the resistor in shape but it is polarized. You must install
it so the white stripe on the diode matches the white stripe on the PCB. Bend the leads just like the resistors and
push it flush onto the PCB. Turn over and solder down the leads and cut the extra length off.
Step 5: Install the Sockets. Sockets are the host spot for the integrated circuits (IC’s). One short
edge will have a notch in it and the white silkscreen on the PCB will have a matching notch. This helps identify
where pin 1 is on the chips. When installing the socket onto the PCB, make sure you match the notch up with
the PCB drawing of the notch. Hold the socket flush on the board and flip the board over. Carefully set the
board down so that the socket remains installed on the board. Solder two opposite corner pins and flip the board
over and make sure that the socket is still flush on the board. If not, you can heat the pin up and push the socket
flush. Solder the rest of the pins down. Repeat for the remaining sockets. Check your work before moving on.
One of the biggest issues with kit building is missed solder spots. Make sure you solder every pin correctly.
Step 6: Install 40 pin headers. There are 3 40 pin IDC .100” spacing headers on the
mainboard. One is used for expansion; the other 2 are for connection to the front panel. The shorter side gets
inserted into the PCB. Make sure it is inserted all the way, hold the connector and flip the board over. Solder
one pin on each edge and check to make sure the header is still flush with the board. Finish soldering the rest of
the pins. Double check all the pins before soldering the next header. There is no polarity on the headers and they
can install in either direction. Just be sure that the longer leads are pointed up.
Step 7: Install the ceramic capacitors. There are 12 .1uF capacitors and 2 of the 22pF capacitors.
Logically, there are 2 that are different from the others and that’s the easiest way to tell the difference. They are
not polarized so you can install them in either direction. You should be able to mount these flush with the board
and then solder them down. Cut the extra length off of the leads after soldering.
Step 8: Install the DC Power Connector. Make sure the hole for the wall wart power supply is
facing the edge of the board. It is easier if you bend the leads away from each other then flip the board over to
solder them down.

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Step 9: Install the Composite Video Out connector. Make sure the yellow post portion is facing
the edge of the board. Mount it flush and bend the leads to hold component in place. Flip the board over and
solder down.
Step 10: Install the PS/2 keyboard connector. When installing the PS/2 connector, take your time
and get all the pins lined up correctly. Make sure the connector is flush with the PCB and flip the board over.
Check to make sure you get all connectors soldered correctly with no solder bridges.
Step 11: Install the VGA connector. This connector fits with ease onto the board. Be sure
to check for bent pins before inserting into the PCB. Flip the board and solder all the leads including the two
large mounting tabs. This will help hold the connector onto the PCB better.
Step 12: Install the Electrolytic Capacitors. These capacitors are polarized and must
be installed in the correct orientation onto the board or you will damage the capacitors and the board. Look at
the large 100uF capacitor and you will see a – (negative) sign on one side with an arrow. That is the negative
lead and is the shorter lead. The other lead is the + (positive) lead and is longer. Insert the capacitor with the
longer lead at the + marked hole on the PCB and push the capacitor flush onto the board. Flip the board over
and solder both leads and cut the extra length away. Repeat for the 2 smaller 10uF capacitors.
Step 13: Install the Voltage regulators. Voltage regulators convert voltage and supply a steady
supply to the IC’s. There are 2 of these and it is important that you do not get these mixed up or damage will
occur to the board. One is labeled 7805. This one is closer to the DC power connector. Install through the 3
holes and then bend the regulator over so that it is laying down flat on the PCB. The hole should match up with
the large hole on the PCB. Place one screw threw the hole and put one nut on the bottom side of the screw. Do
not over tighten the screw. Solder the 3 leads and cut the extra lead lengths off. Repeat for the 3940 voltage
regulator.

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Step 14: Install the IC chips. Find the chip labeled ATMEL ATMEGA8515. This is
the main CPU chip of the Altair 8800 micro. One short edge will have a notch in it. Match the notch on the chip
with the silkscreen or socket on the PCB and carefully install the chip. The machined sockets are going to give
resistance to installing the chip so use caution not to bend the leads. If you do, remove the chip and straighten
out the pins and try again. Repeat this step for all of the chips making sure to install them in the correct
orientation. You are now finished with the mainboard and are ready to move on to the front panel.
Inventory your parts for the front panel from the following list:
PART # QTY
2 POSITION SPST SWITCHES 21
3 WAY MOMOMENTARY TOGGLE 3
220 OHM RESISTORS 32
4.7K OR 3.9K OHM RESISTOR PACKS 3
HEADER CONNECTORS 2
RED LED's 32
FRONT PANEL PCB 1
SCREWS 4
While the parts list looks small, the front panel is much more difficult to build than the mainboard. The front
panel PCB assembly will require the front panel plate to install the switches and LED’s so they line up with the
holes correctly. Find your bag with the front panel components and check your inventory.
Step 1: Install the resistors. There are 32 resistors and they are all 220 ohm resistors. They are
labeled RED, RED, BLACK, and GOLD. Install and solder them the same as the mainboard.
Step 2: Install the resistor packs. These are polarized and must be installed in the correct
orientation. Look for the small dot on the edge of the resistor pack. Match that dot with either a dot on the PCB
or the same edge as the RPx label. Solder all the leads and double check your work.