Building a REX

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Building a REX

This is a version of Steven Adolph's REX Classic with a modified PCB design.
It is electrically identical to REX Classic, and uses the REX Classic firmware & software.

The PCB layout and shape are modified to:

  • snap into a 3d-printed carrier to fit the Molex78805 socket
  • provide connections for power and PORT_EN for programming the CPLD

Original version of this page, for building the original REX1

PCB Source
Carrier Source

Parts & Materials

Note if ordering from PCBWAY: On the order page, you may have to manually change "Min tracks/spaces" to "6/6mil"
All tracks & spaces are well over 6 mil (everything is 0.2mm which is almost 8 mil), and that setting drops the price from $50 to $5

ENIG adds a lot of cost on PCBWAY and JLCPCB lately.
Currently the cheapest way to get an ENIG version for gold contacts (other than OSHPark) is Elecrow.
Upload the gerber zip from the releases, and manually select ENIG and Castellated Holes, and just use the cheapest shipping.

Other Compatible Flash Chips and how to identify them


Cheap Chinese clone is fine.
Look at the pictures for ones that say model DLC9G, or DLC9LP. Don't put "DLC9G" or "DLC9LP" in the search, you will only get the overpriced ones.
Get one that includes a "flying leads" cable, with separate loose individual wires on one end.
A cheap usb-ttl cable is perfect. It's cheap, and already ends in loose wires with female dupont pins.
Just use the red and black wires and ignore the rest.
  • PC with at least one usb port, and a COM port or usb-serial adapter.
  • Sandpaper, medium grit (120 or so), and a hard flat surface like a cutting board.
Do not necessarily need anything fancy. I actually used this exact one to build a few REXs, although now I use a Hakko FX-888D with a T18-C2 tip.
Or the strongest reading glasses you can get at a local drug store. 3.00x or higher.
0.1" (2.54mm) pitch single row male pin header
one shunt

  • A Tandy Model 100, 102, or 200.


  • Xilinx ISE 14.7 Lab Tools
Lab Tools is a subset of ISE. You can use either ISE or Lab Tools, but you only need Lab Tools to program the REX.
This software is old and needs special futzing to make it work, no matter what OS you are using.
Installing on Ubuntu Linux
Installing on Windows.
There are several tpdd clients, and several ways to get one installed. These are a few options:
For Mac, Linux, FreeBSD, any other unix: Get dl2 and use the bootstrap option to install TEENY.100 or any of the other options listed by "$ dl -l"
For Windows: Get tsend.ps1 and use it to install TEENY.100 or any of the clients found at
Play File:DOS100.CO.MP3 into the cassette port to install TS-DOS. (SOUND OFF:CLEAR 0,57089:RUNM "CAS:DOS100.CO")
Get a real tpdd and bootstrap it's utility disk to install "Floppy".
For Mac, Linux, FreeBSD, any unix: dl2
For Windows: LaddieAlpha
Start there, and follow the links to whatever is the latest "REX Release x.x Rebuild Package" zip file.


Prep the Bare PCB

Lay a piece of medium grit (100-200) sandpaper face up on a hard flat surface like a cutting board.

Sand the edges of the PCB on the sandpaper just enough to clean off the panelization break-away points.

Use magnification to look closely at the castellated edge contacts for copper or gold "flags" hanging on the edge of most contacts. Scrape them off with an xacto knife.

Solder the Electronic Components

Solder these parts onto the matching labeled locations on the pcb.

U1 = XCR3064XL
U2 = 29F800
U3 = LP2980-3.3
R1 = 10K
C1 = 1uF
TP1 & TP2 = right-angle pin (optional)

Don't be too intimidated by the tiny legs on that TSOP-48 chip.
Just use magnifying glasses, lots of flux, and the DRAG TECHNIQUE.
Another example:

The TP1 and TP2 pins are only needed if you think you will ever perform the hardware modification required to use the main rom management feature. See FlexROM_100 or FlexROM_102 to facilitate this.

Clean the Finished PCB

Even "No-Clean" flux should still be removed as much as possible after soldering.

The best is to use an ultrasonic cleaner and saponifying pcb cleaning solution.

If you don't have that, then at least make sure your flux and solder are both "no-clean", and then use 99% isopropyl alcohol and a brush. This will still leave flux trapped under the chips no matter how much you soak it or wash it, but for no-clean flux it's not ideal but ok.

Program the CPLD

Now we need to flash the CPLD (Xilinx) with the .jed file. This configures the blank CPLD into a functional circuit that actually does something.

  • Get the .jed file from here.
  • Connect the jtag, 5vdc, and PORT_EN jumper.

Snap the PCB Into the Carrier

Flash the Firmware

Follow the REX 4.9 update directions to load the firmware onto the REX.
The original directions for that are here: 4.9 update directions.

Here are explicit/literal example directions to do that using dl2 on a Mac, Linux, FreeBSD, or other unix pc.

(For Windows: instead of dl2,

Download & unzip the various files manually with a browser instead of cutting & pasting the wget & unzip commands.
use tsend.ps1 for the bootstrap in place of "dl -v -b FILE.100"
use LaddieAlpha for the TPDD server in place of "dl -v -u")

Back up any files off of M100. M100 will be wiped.

Cold reset the M100 (ctrl+pause+reset)

Power off the M100

Install the REX in the M100's Option ROM socket

Connect the serial cable between M100 and PC

Power on the M100

Install dl2 on a PC:
On the PC, in a terminal window.

$ git clone
$ cd dl2
$ make all && sudo make install

Install TEENY onto the M100:
On the PC:

$ dl -vb TEENY.100

Follow the prompts on the PC and on the M100 screen...

On the M100:


On the PC:


On the M100:

Look at the Top: ##### number.
A 32k machine should say 62213.
Yours may say something else.
Use that number in the following CLEAR command.
CLEAR 0,62213

On the PC:

should be back at a shell prompt now

Download the REX Classic setup files

$ mkdir rex_setup
$ cd rex_setup
$ wget
$ wget
$ unzip
$ unzip

Use dl2 to start a TPDD server

$ dl -vu

Copy RF149.CO to the M100, then run it.
On the M100:

should be at menu
> L RF149.CO
> Q
should be at menu
CLEAR 0,55000
should be at menu
run RF149.CO
Answer Y
should be at menu

Reset the M100 to clear out TEENY and RF149.CO

should be at menu, ram wiped

The flash memory on the REX is now formatted and loaded with REXMGR and a TS-DOS option rom image.

Install REXMGR from the REX itself

CALL 63012
should be at menu, REXMGR should appear in menu

REX is now ready to use, and empty except for TS-DOS.

Now install an option ROM image. Example: Ultimate Rom II

press TAB once
screen should say "TS-DOS* ------"
press right-arrow once, highlight should move to "------"
press F2
Loading from image filename: UR2100
Hit any key when TPDD ready.
Loading 0:UR2100.BX     ####
now it should say "TS-DOS* UR2100 ------"

UR2 is now loaded into REX, but not currently selected/active, TS-DOS is.
What this means is, If you were to go back to BASIC and run CALL 63012 right now, it would load TS-DOS, as if you had a TS-DOS option rom in the option rom socket.
To run UR2, you have to select it in REXMGR first.

right-arrow to highlight UR2100
press enter

UR2 is now the active option rom image. Additionally, the equivalent of CALL 63012 was already done for you by REXMGR just as a convenience to skip a step.

F8 back to menu.

Leave dl2 running on PC while you load more rom images.

Ctrl+C to exit dl2 when you're done with it.


That was the last step. You're done! Consult the REX docs to start using it!

Main ROM Management

Main ROM Management


KiCAD source files for the PCB

OpenSCAD source files for the carrier

Version c6 pcb This version of the pcb is obsolete, but has pics of the firmware flashing process.

Version c8 pcb This version is also now obsolete, but the only difference is the pcb dimensions and matching carrier.

User Manual

Original sources and support files from Steven Adolph

Backup copies of some of the sources and support files