Installing and Operating the Antique SWTPC 6800

by Jim Billiter – September, 2004 [email protected]

A. Unpack and inventory the components. 1. Do not plug in or apply power until instructed below. 2. Inventory of major components: - SWTPC CT-1024 terminal in custom wooden housing - Panasonic 9” video monitor – TR-920M - SWTPC 6800 System - SWTPC AC-30 cassette tape interface - Documentation: yellow binder++ - Two cassette program tapes - Three spare 2102 SRAM ICs (16-pin DIP chips) - Three audio cables

B. Connect the hardware components. 1. Connect the gray cable from the AC-30 labeled ‘A’ to the 25-pin (DB-25) connector on the CT-1024 terminal housing labeled ‘A’. 2. Connect the gray cable from the 6800 computer labeled ‘B’ to the DB-25 connector on the CT-1024 terminal housing labeled ‘B’. 3. Connect the white coaxial video cable from the CT-1024 to the rear of the Panasonic video monitor.

C. Set the switches. 1. CT-1024 - Power to OFF (left position) - Page to 1 2. Panasonic video monitor - 75 ohm (switch on rear) - Power to OFF (inside front panel) 3. AC-30 - Switches on top cover – both to 300 Baud - Power to OFF - Rem/Loc to Rem - Status – both centered - Read select to A - Record select to A - Manual/Auto to Manual

D. Power up. (Power down in the reverse sequence.) 1. Plug in all four major hardware components. 2. Switch Panasonic video monitor’s power ON and wait 15 seconds. 3. Switch CT-1024’s power ON (switch position right) and use the video monitor’s controls to see stable and legible, but meaningless characters on the screen. 4. Switch AC-30 power ON. 5. On the 6800 firmly press and release the large red POWER button. An asterisk should show on the video monitor, indicating the control program (MIKBUG) is awaiting instructions. Poke ‘R’ on the keyboard and MIKBUG should display the 6800 ’s registers.

Good work. Enjoy.

1 Operating Notes

Custom Switches

The two switches atop the AC-30 Tape Interface have little to do with the AC-30 itself. The switches are used to change the computer and terminal between 300 bps operation and 1200 bps when running BASIC. The computer has two serial ports: #1 (control) is configured for 300bps RS-232, and #3 for 1200 bps. MIKBUG and tape operations are constrained to use only the control port (#1) at 300 bps. But BASIC may use either port #1 or port #3. To change BASIC’s port just use the ‘PORT=x’ command and throw both switches to the appropriate speed.

Loading Cassette BASIC

- Use the ‘Backup’ cassette tape; the original distribution from 1976 is bad in part. - Cue the tape to the beginning of the second marking tone about 30 seconds from the beginning. - Connect the cassette player to the AC-30 by an audio cable between the cassette’s earphone jack and the AC-30 ‘A’ EAR jack. - Set the cassette volume to about ¾ of full. (You may need to experiment with other volume settings.) - Set AC-30 switches as at installation (above). Status lights should be OFF. - Type ‘L’ at the MIKBUG prompt, and observe the AC-30’s Read Ready indicator turn on. - Play the tape, and observe the AC-30’s Read Data light turn on (varying intensity) when data flows - After about 13 minutes the AC-30’s Read Ready light will turn off and MIKBUG will return to its ‘*’ prompt at the terminal. - BASIC is loaded. Type ‘G’ at the MIKBUG prompt and BASIC should prompt with ‘READY #’. Using a Modern PC As a Terminal and Data Source/Repository

It is possible, and often desirable, to replace the CT-1024 terminal and the AC-30 tape interface with a modern personal computer. The author recovered SWTPC Basic v2.0 from the Flex Web site using this technique.

Michael Holley’s excellent Web site has detailed instructions for this exercise: http://www.swtpc.com.

[Beware: the author used a standard RS-232 breakout box to breadboard Michael’s cable. Michael’s instructions were fine, but I wasted quite a bit of troubleshooting effort before I discovered the breakout box’s pin 7 (signal ground) switch was always ON, even when set to OFF.]

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