IOB6120
Multifunction companion board
for the Spare Time Gizmo's SBC6120

Hardware emulation of numerous DEC PDP-8 options, and lots more!

  • CompactFlash™ interface

  • 2MB nonvolatile ramdisk

  • VT52 terminal with output to a standard VGA monitor and input from a standard PS/2 PC keyboard.  The VT52 can be set as the console device by a jumper, and the SBC6120 serial port becomes another SLU.

  • 3 serial ports (SLUs) compatible with DEC KL8JA (RS232C)

  • Printer Port compatible with DEC LC8E with buffered Centronics parallel output

  • Crystal Clock DEC compatible timer device

  • 36 digital I/O pins that can be individually configured as inputs or outputs

  • Complete Flexibility due to its FPGA implementation; IOB functions may be enhanced, removed, replaced or added.  For example additional serial ports or a front panel interface could replace some of the digital I/O pins.  Using free Xilinx VHDL synthesis software, the 100K-gate FPGA's programming can be altered and tested. Currently, only 70% of the device is used for all the functions listed here.

  • Flash ROM used to store OS extensions and FPGA programming; 128-384KB free for other uses.

  • Clock/calendar (optional) battery-backed year/month/day hour:minute:second clock

  • Speaker (audible bell)

  • Enhancements to BTS6120 (see below)



Here is the manual in PDF, and here are the design, software and documentation files: current_version (~1.8MB).
(the filename of the current version reflects the BTS6120 version, the extension ROM version and the FPGA code version)
This device's design is made available under the terms of the GPL.

There is lots of reusable, fairly modular VHDL IP in there - a configurable UART, PS/2 keyboard to ASCII, ASCII to VGA video, serial terminal and other good stuff.  It's mostly wrapped in code that interfaces it to a PDP-8 bus via IOT's, but it's not specific to that bus.

The construction of the board is straight-forward, but since it is built with surface mount components, good  tools and some practice are strongly recommended before tackling it.  Most parts are half pitch (0.05" lead spacing), and are easily solderable with a fine-tipped temperature controlled iron and fine solder.  A few parts are fine pitch (0.5mm lead spacing) and can be difficult to solder without strong magnification and a steady hand.

I AM OUT OF PCBs AT THE CURRENT TIME - NOT SURE WHAT THE REORDERNG PLAN IS YET

I can provide bare printed circuit boards, kits of parts and assembled and tested boards.  Delivery times depend mostly on the whims of my parts distributors.

Bare printed circuit board.  4 layers, solder mask and silkscreen. $  28.00
p.c.b. and all parts except batteries and SBC connector $ 110.00
Assembled and tested (without batteries and SBC connector) $ 171.00
kits or assembled without ramdisk and/or serial and/or parallel and/or CompactFlash
(note: this board and the Spare Time Gizmos ramdisk cannot coexist even without the ramdisk installed on the IOB6120)		  Ask
Updated SBC6120 EPROMs and GAL (the updated GAL adds the ability to use the VT52 as the console).  This revision works with a stock SBC6120 as well, so there's no need to have both this one and the older version.
*NOTE* newer SBC6120's do not require updated firmware - check for EPROM version 266 and GAL version IOT1B.		 $  18.00
$   8.00  if 27C64/256's and GAL22V10 provided (e.g. programming only; swap with existing parts).  If you have your own programmer, the data files are provided in the design package above.
clock/calendar option (kit or assembled)
(note: OS/8 does not support this option, but application programs may access it)		 $   6.50

All prices quoted are without MA sales tax, if applicable, and shipping charges.   Order

Changes and Enhancements to BTS6120

These are implemented in the revised SBC6120 EPROM set, and are useful even without an IOB6120.  The revised EPROMs are larger than the originals, so 27C256 or 27C512 EPROMS must be used instead of the 27C64's that were originally specified.