Loading And Using 4K Basic From Paper Tape - Altair 8800 Clone Operator's Manual

B. Loading and Using 4K BASIC from Paper Tape
In this demonstration, we will load 4K BASIC Version 3.2 from paper tape. In
the mid-1970's, a teletype connected to single serial port on the Altair
would have served as both the console and paper tape reader. We will dupli-
cate this configuration using a terminal emulator on a PC as both the console
and paper tape reader.
Computer Configuration
For this exercise, serial port #1 on the Altair Clone (the upper DB-25
connector) should be configured as a 2SIO port at octal I/O address 20/21.
This is a standard Altair configuration. This is also the default Altair
Clone configuration. You can confirm or change the Clone's serial port
configuration if needed. See "Serial Port Menu" in Part 2, "Configuration
Monitor" of this manual.
The default baud rate for the serial port on the Clone is 9600 baud. While
this is much faster than the 110 baud at which a real teletype operates,
we recommend using 9600 baud for this demonstration. Buffering in the PC's
serial port drivers and issues with some USB-to-Serial adapters can make
operation at 110 and 300 baud problematic.
Terminal Emulator Configuration
The TeraTerm terminal emulator is used to duplicate the functionality of a
teletype. Confirm serial settings of 9600 baud, 8 bits, no parity, one
stop bit (8N1) in the "Setup->Serial Port" menu in TeraTerm. Also confirm
that the "Transmit Delay" fields are both set to zero.
To load 4K BASIC, we must first enter a small program via the front panel
called a "bootstrap loader." The job of the bootstrap loader is to receive a
second loader from paper tape called the "checksum loader." The checksum
loader is at the beginning of the BASIC paper tape. Once the checksum loader
has been read into memory, the checksum loader then reads in BASIC from the
remainder of the paper tape.
The code for the bootstrap loader is provided by Altair in the BASIC manual.
Different versions of the bootstrap loader are required based on the version
of BASIC and the type of interface card being used. For this demonstration,
we need the bootstrap loader for the 88-2SIO serial board and for 4K BASIC
Version 3.2. Following is the bootstrap loader code for this combination of
BASIC and serial port type:
Addr Data
---- ----
000 076
001 003
002 323
003 020
004 076
005 025
006 323
007 020
Follow these steps to enter the bootstrap loader:
1) Turn the power switch on.
2) Raise and hold the STOP switch in the STOP position, then raise and re-
lease the RESET switch. Finally, release the STOP switch. This performs
a hard reset on the computer and sets all address lights to zero.
3) Put the first data byte in switches 7 through 0, then raise DEPOSIT.
Addr Data Addr
---- ---- ----
010 041 020
011 256 021
012 017 022
013 061 023
014 032 024
015 000 025
016 333 026
017 020 027
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Data Addr Data
---- ---- ----
017 030 300
320 031 351
333 032 013
021 033 000
275
310
055
167