Last updated: 21 June, 2016
The HCS II was first presented in the February 1992 issue of Circuit Cellar Ink. It's primary purpose is low-cost, do-it-yourself home automation, but with some imagination, it can be used to automate and monitor just about anything you like.
The HCS II is a central controller, with a number of daughter boards: Some plug into its vertical stacking bus though a pair of connectors, while others are wired through an RS-485 half-duplex network. The daughterboards expand the capability of the HCS II from supplying more digital I/O through to text-to-speech and DTMF control. It's also capable of switching on and off heavy loads through relay boards, analog sensing (such as temperatures and lighting conditions) and X-10.
Although the HCS firmware and associated programs are GNU GPL'd, it is still very much copyrighted by Circuit Cellar. Some information found here is reproduced with permission of Circuit Cellar Inc.
The information found on this page was obtained from various sources: manuals, the Circuit Cellar BBS and its successor sites, USENet and correspondence with HCS users.
This site is dedicated to documenting detailed technical info on the HCS II as a service to the community. No support is otherwise given. For general help on the HCS II, check out the Circuit Cellar website.
Where can I get help for my system?
The best reference for the HCS are the collection of articles written in Circuit Cellar years ago. Anything referring to the HCS II is exhaustively written about there.
What does the HCS II consist of?
From a hardware standpoint, the HCS II consists of one of four types of Supervisory Controllers:
The third controller had some interesting bits to it. The SpectraSense 2000 and to a greater extent the RTC180 and the HCS II DX boards had a great deal of expansion capability:
(Remember that the HCS II uses a half duplex [two-wire] RS-485 network best configured as a daisy-chain.)
All of the modules above had the capability to be programmed to work in a stand-alone, embedded manner. What made them work together was the presence of an RS-485 port and chip plus the software to make that work.
HCS II DX and RTC/HCS180 stackable expansion
The FCC-approved SpectraSense 2000 was targeted at dealers and installers wanting to get into the home automation market using the HCS II. More on that is located here. Essentailly it combined some of the boards and features listed above into a single board mounted in a panel.
Later, Circuit Cellar released some enhancements to the HCS II:
Creative Control Concepts had the following product line in addition to the above after acquiring it from Circuit Cellar:
Some users have also created their own add-ons as well.
So much for the hardware. In terms of software, all the modules above including the supervisory conotroller boards had custom-made firmware. The COMM-Link however worked from a common code-base, similar in spirit to the common hardware base they represented.
However there are several DOS, Windows and Linux-based tools that were necessary for HCS II operation. First, the Circuit Cellar releases:
Beyond that, a small number of users released front-end replacements of HCS Host with some other tools:
I want to build an HCS II Module. Where do I start?
There are a handful of sources that document the HCS II serial protocol. The best place to start would be the HCS II documentation itself, followed by Mike Baptiste's overview and example in the September 1999 issue of Circuit Cellar magazine. His PIC-DIO is the center of attention.
What are the power requirements of all these boards?
Both the HCS II DX and the original RTC180-based HCS II take approximately 150mA @ +5V. All the boards have 5VDC voltage regulators allowing one to standardize around 12VDC wall-wart type transformers or by feeding 12VDC through twisted pair (Be careful NOT to exceed amperage ratings!).
Are there any 'gotchas' for powering all this?
None really. But, Mike Baptiste also wrote quite a bit about that in the January 2000 Circuit Cellar. Michel Clavette also built a UPS circuit to backup the HCS.
Why are you calling it HCS II instead of just HCS or HCS-II or HCS2?
It is called the HCS II because the original HCS was presented by Steve Ciarcia in an issue of Byte Magazine dating back from the early 1980's. Also as Ken Davidson (the principal designer and developer behind the HCS II) once said, "it's called HCS II."
Who wrote the ROM?
Ken Davidson is the ROM's original author. Jack Gansle pioneered the RTOS code for the HD64180 that was later to appear in the HCS II ROM code. Jeff Bachiochi then took over later development before Mike Baptiste last commercially supported it.
How big is the ROM?
The ROM is housed in a 27256 or equivalent EPROM, which is a 32KB device. Currently the compiled code sits very comfortably in the EPROM.
What compiler is used for building the HCS II ROM?
The HD64180 cross-assembler from 2500ad was used. The company has since been bought by Avocet, and lives on in the ADX product line. There's a 20% hobbiest discount for the cross-assembler. Sticking to this cross-assembler, while expensive, saves on having to port the code to other cross-assemblers and keeps and CVS repository pure.
What other cross-assemblers can I use?
If the Avocet assembler isn't desired, there are a couple of other possibilities:
What is the correlation between the hardware names and the naming in the XPRESS language for the HCS II SC variants?
In XPRESS 2.0, the
CONFIG SC = arguments are listed as follows:
|RTC180, RTC-BUFIO or RTC-BUF50||SC2|
|BCC180, BCC13, BCC54||SC4|
|BCC180, BCC30, BCC54||SC5|
In XPRESS 3.0 and up, the
CONFIG SC = arguments are listed as
So as one can see, the supervisory controller options were streamlined a bit. This was the result of writing extra code which probed the hardware to see what hardware was accessible through the system bus. (Very much in the same way that Linux tries to autodetect hardware and install the appropriate device drivers.)
Help! Why does my PL-Link hang? Or, why is the TW523 module's LED blinking fast? Or, why is the LED on the PL-Link not on?
The PL-Link, which is the X-10 gateway for the HCS II system, can sometimes hang due to a power supply glitch, or more commonly, because of a loss of electricity - sometimes a rapid on-off, other times a prolonged duration. This can be visually observed by looking at the TW-523 module and noting the rapidly flashing red LED. This isn't the normal behaviour. The PL-Link's on-board LED should also be blinking normally, and if it isn't, probably is stuck.
From a technical viewpoint, what is happening is the PL-Link is freezing in transmit mode because the reset circuitry hasn't generated a true reset on the board.
There are three solutions to this, one temporary, one permanent and one avoiding the whole thing altogether:
The third option has the added bonus of taking traffic off the RS-485 network and getting the X10 status back quickly given that the PLIX is running off the HCS II SC stack connectors. Of course the downside is running yet another board on the stack which increases the current draw of the whole set of boards (which in turn really starts to cook the regulator on the HCS II board.
I'm having more and more problems with my PL-Link, despite having double checked my modules, swapped them out for 'pro' versions, etc. What do I do?
In the early days of X-10, all one had to worry about was whether household wiring was divided into two legs therefore looking at using a signal bridge as a solution. One other problem that sometimes arose was signal corruption as the X-10 signal made it's way to the street transformer.
These days, the biggest culprit is now likely to be the introduction of inductive loads, like CFL lights. Delving into this is beyond the scope of this website, but here are three mentions of what the problems and possible solutions are:
I have an HCS-PLIX, or I want to build one, but can't source the parts?
NTE makes the Motorola 6821 PIA used in the HCS-PLIX. It's available through their distributors. The PLIX chip is still available from Micromint.
Are there any watchdog circuits on the HCS II SC?
There are no watchdog circuits built-in to the HCS II SCs. However, in an article printed in the January 1995 issue of Circuit Cellar Ink, Steve Ciarcia described a couple of watchdog circuits that can be added around the HCS II.
What about Y2K problems?
Y2K wasn't that huge of a problem with the HCS II for the most part, since XPRESS dealt with 2-digit years. However, Mike Baptiste made some useful observations:
Early HCS-II boards (and probably RTC180s with older SmartSockets) used DS1215/DS1216 chips. This chip handles 2000 OK but it will NOT treat 2000 as a leap year. The cheap fix - reset your clock on March 1st (not sure if it will let you set it to 2/29/00 - haven't tried) Or, you can replace your DS1215 with a DS1315 that handles the 2000 leap year. If you have an RTC180, you'll have to replace your smart socket (not cheap) if it has an older DS121X chip in it. If you want a DS1315, let me know - I have plenty. $9.95 (shipping included) Before you think I'm gouging, check your electronic catalogs. These chips are not cheap.
XPRESS deals in 2 digit years and is OK though the published Y2K baseline is v3.6 Note you need to ensure your XPRESS code doesn't have a Y2K bug in it like IF YEAR > LASTYEAR THEN
HOST had a problem with setting the time in 2000. A new version available on the website (v3.62) will solve this problem and can be used with XPRESS v3.x Not sure about v2.x - haven't tried that yet.
The best test you can do is set your HCS clock to Dec 31, 00 and let it roll over. Try fooling around with XPRESS time/date commands with the date set to 2000 and see what happens. Most users who have tried this have reported no issues though I don't know which versions they were on. The XPRESS firmware change history shows no mention of any Y2K specific fixes though that doesn't mean there were any.
What protocol does the HCS II use to communicate with its modules?
The HCS II uses RS-485 for the network signalling to connect over a twisted pair with the other modules. The HCS II then uses ASCII packets for the inter-module protocol communications. This is outlined in an article by Mike Baptiste in the September 1999 issue of Circuit Cellar.
Is there a right or wrong way to building an RS-485 network?
A typical RS-485 network is built in a daisy chain manner. However, over the years many HCS users have opted to build their networks in a star configuration. The risk in doing this is that reflections on the network can turn up if terminations aren't properly done, since there's meant to be a termination at each end of a cable run.
Speaking of termination, there should only be two terminations activated on the network at once and preferably on the end of the longest cable runs. Also, somewhere along the network, pull-up and pull-down resisters (found on all the COMM-Links) should also be activated, again typically where the terminators are located. This keeps the HCS RS-485 network in a stable state.
If you intend on using a star configuration, or a hybrid of star and daisy chain, then experimentation on the placement of the terminators is required. Also, the location of the pull-up and pull-down resisters in the network can differ according to most people's experience. Again, experiment with these and don't be surprised if the network behaves better despite them not being active where the termination resisters are.
Further info on RS-485 network guidelines can be found here. This document quietly got inserted in later printings of HCS module technical manuals.
Do the Micromint RTC180 boards work as a replacement for the HCS II?
According to pictures of the early versions of the HCS II, it appears that the RTC180 was in fact used as the original HCS II supervisory controller. There are some key differences between the RTC180 and the HCS II DX that came out later (as part of a Circuit Cellar Ink magazine promotion):
As far as backing up memory is concerned, the best way to do this is through the use of a Dallas Semiconductor SmartSocket, which features on-board batteries in a 28-pin DIP. Also, if you wanted to back up the log memory, using this socket for that makes sense as well.
Is there a replacement for the HCS-Voice board?
Indeed there is. Jeff Bachiochi presented such a replacement and interface using Winbond's ISD2500 series chips in the April 1994 (#45) issue of Circuit Cellar Inc. Winbond recently produced a migration document in 2007 to move from the ISD2500 series to the ISD1700 series.
What's this about bus timing affecting HCS II operation?
Originally, the HCS II was created with an HD64180 chip running at around 9MHz.
Mike Baptiste then found a way to double the speed using the existing crystal
by swapping in a Z80S180. Depending on the XPRESS program written and the
number or type of boards on the stacked bus, it was possible that the HCS
could lock up or transmit corrupted information to
The solution was to swap out most all the LS logic for the 74F family logic
except for the 7425 IC.
Speaking of time, what about the purported timing drift in the system's time?
The HCS II uses a DS1315 as its RTC, which it polls every time the HCS SC
status update is sent to the
host program. Those who ended up
building the HCS II SC from scratch (or even via the free magazine PCB
giveaway) found themselves with unstable clocks: For example, either a
gain of 3 minutes per week or a loss of a minute over the course of a
month, whichever. As it turns out, many Dallas Semiconductor parts used
crystals (32.768kHz) with a load capacitance of 6pF. Many common crystals
can use 12.5pF or 20pF crystals, making this out of spec. The gory details
of this can be found in Maxim's Application Note #58.
The solution? Swap the crystal.
What about the Micromint BCC180?
As a matter of fact the BCC180 is known to function with the HCS ROM as well. Steve Ciarcia himself ran the HCS II ROM using a BCC180, plus a bunch of BCC expansion boards for controlling hardwired links. (Steve's preferred method of running his house is using hardwiring, as opposed to exclusively using X-10.)
What is a COMM-Link?
A COMM-Link (or Comm-Link) is a common processing, RS-485-networkable platform that can be adapted for any HCS II purpose. A good analogy is a common automobile chassis upon which different models can be built. There have been two types of COMM-Link:
It should be noted that the 8031-based COMM-Links came in two generations: The first generation boards were simply called COMM-Link on the silkscreen and are easily identifiable by the prototyping area of the board, and the different layout of the LEDs; The second and more common generation is the one lacking a prototyping area and has COMM-Link2 written on the silkscreen.
Circuit Cellar then came out with the AnswerMAN device, which is an embedded PIC-based device that can fit neatly into a 28-pin socket footprint. This device was designed to take on most of the COMM-Link designs and combine them into one common footprint. John Morley's WeatherNode project is a good example of this.
While the PIC is newer and more compact, there's absolutely nothing wrong with using the original COMM-Link designs. The point is that anything can be called a COMM-Link, so long as the HCS II ROM knows how to deal with it. Also, the single biggest advantage to the original design was it's cookie-cutter approach: Improvements to one COMM-Link board could very well be ported to the others. Beyond that, parts for 80C31/0831-based COMM-Links continue to be available in a consistent manner, whilst the PIC-based designs seem to suffer from having their primary component, the PIC itself, become obsoleted by other parts. (This can in some cases make for challenges in incorporating the new part in the old design.)
Examples of 8031-based COMM-Links have been:
Some examples of PIC-based COMM-Links:
By far one of the biggest advantages of using the original COMM-Link design is their flexibility to be redeployed as another type of -Link. For example, some users have converted extra PL-Links to MCIR-Links with the swapping of a few parts and the EPROM. The PIC-based designs were very targetted to their purpose, and ironically for being more modern parts, haven't really stood the test of time as well.
Which Network modules are supported directly by the ROM?
Today only six are defined as directly supported:
Plus two reserved bytes for future expansion. Note that the AMAN has taken the place of the ADIO-Link, DIO-Link and DIO+Link combined, despite still having 'slots' reserved for some of them.
What about the Micromint BCC series boards?
As described elsewhere, the Micromint BCC series boards can work with the HCS II ROM. Boards supported are the BCC54, BCC30 and the BCC180. They are still available from Micromint.
Is the COMM-Link source code really in the Public Domain?
This is a misconception based on the original filename of the zip'd source code. The 'public' in the filename denotes the fact that the source code was cleaned-up of documents like internal memos and such and commented. Thus the word 'public' really means, "for public consumption". Circuit Cellar still retains copyright (and other contributors hold their own) despite being licensed using the GNU GPL.
In what languages is the source code for all of this written in?
The HCS II and its modules are written in the following languages and tools:
Host: Borland C 3.1, using a large memory model;
compile: Borland C 3.1, using a large memory model.
process: Borland C 3.1, using a large memory model.
Note that both the
were written in a manner that made them portable to be compiled on almost
any C variant, making them available to Linux as well.
The user-contributed or original designs also varied:
Why were PICs used for the subsequent generation of COMM-Links?
Mike Baptiste created these modules around the PIC because that's what he was familiar with. He later on sold these under the Creative Control Concepts name.
Why can't my Generation-1 COMM-Links remember their module number?
The old COMM-Links (and even some of the later PIC-based designs) didn't have any NVRAM, flash or battery-backup on board the modules. If power was lost, they would default to module number 0. The only way to resolve this is to install a Dallas/Maxim SmartSocket in the socket of U3, followed by the static RAM.
What has been the bone of contention for the HCS II? What do I do about my log memory?
By far the single biggest complaint is related to memory - or a lack of it. Despite the Z80180 processor being able to access 1MB of RAM, it can only do so using bank-switching techniques. Unfortunately, there are no free memory windows due to the fact that the 64K memory segment has been split in two: One half for the events program and the remainder for log memory.
The other issue, which is pressing from an aesthetics and accessibility viewpoint, is that the stacking bus of the HCS II doesn't lend itself to a standard enclosure or panel. As a result, the panel could get very expensive if you're looking for a 4-5 inch or greater depth.
One solution proposed (but never pursued) was to build a COMM-Link that would accept logging from the HCS II via the RS-485 network. The biggest advantage of this was that the HCS II could be brought down without losing logging data, and the "Log-Link" could be whatever design was chosen. (In theory this would have been nothing more than a sniffer monitoring events going across the RS-485 network, but it wouldn't be privy to the HCS-II's on-board I/O.)
Other ideas included:
(If you believe the last point is a kludge, realize that many customers of industrial building automation systems have run into the same thing and in response, a number of vendors elected to sell Windows-based servers that monitor existing installations 24x7 through a serial-to-ethernet add-on. Thus the limitation of logging memory was dealt with by selling automatic log data downloading as a feature. If you think about it, this means having the ability to run a number of separate yet identical systems and letting the server poll them each to determine which was what controller and identifying log entries in that manner. All-in-all, it is a win-win for everyone: The vendor makes more money selling a software-based appliance and customers didn't need to swap-out hardware...that is until the vendor convinced them otherwise! In any case, Philippe Printz's WinHCS came tantilizingly close to implementing the concept described.)
Who or what is Creative Control Concepts?
Creative Control Concepts was a sole-proprietorship founded by Mike Baptiste, an enthusiastic and long-time user of the HCS II, which took a license of the HCS product line from Steve Ciarcia and Circuit Cellar. However, within two years, sales dwindled and the company shut down operations. Until December of 2006, it wasn't selling or supporting any HCS II products since mid 2001. As of January of 2007, Creative Control Concepts restarted operations to sell add-ons for the HCS II (but no Circuit Cellar HCS II hardware as it is no longer licensed for that). In any case, the website remained running with HCS II info as a service to the community. There were few products left for the HCS II in it's catalogue. As of mid-2010, it ceased operations for good.
My hardware is dying, what do I do?
As implied above, the Micromint boards are still the primary (and remaining) source. The COMM-Links upon which many of the remotely-connected RS-485 modules are based on can be built from scratch again around the venerable but reliable 8031. However, to save that work, just order an RTC31 from Micromint and an RTC-proto board to layout the work. Or, for the minimalist, just get a board with extended connectors and only the necessary logic for the 8031 to drive.
The other alternative to RTC31 boards is to construct a board around the AnswerMAN module, as this can accomplish most anything these days and is the more cost-effective option. Micromint should still sell AnswerMAN development boards which will also minimize the construction process.
For replacing the Supervisor Controller, the option is to find another one from a user willing to part with theirs, or buy the RTC180 or the BCC180. Note that the RTC180 has a number of disadvantages to it, compared to the HCS II DX board, as described above.
Otherwise, consider looking into other HA systems.
What is the compile program? What is Host? What is Process?
The HCS II uses two DOS-based programs:
events.binfile. This byte-compiled file can then be uploaded to the HCS II supervisory controller using the
Floppy disk distributions also contained an extra demo program called
process, which demonstrated how logdata could be extracted
from its binary format dump file.
compile run under Windows?
Host is known to run under windows 95/98/98se/ME but not under
Windows 2000 or XP. This is because the older versions of Windows allow
DOS-based programs to write directly to the serial port hardware, while
the latter versions of Windows force applications to go through virtual
drivers. There have been sporadic reports that
Host can run
under Windows XP.
compile can run under any version of DOS or Windows.
Can any of this work under Linux?
Linux, using the DOS emulator
dosemu, can run both these
programs without any problem. However,
compile can compile
cleanly under GCC without modification, so
compile can be run
How soon will an uploaded
events.bin take effect.
The effect is immediate while the RS-485-linked modules might lag a second or two, depending on the XPRESS program you wrote.
What versions of
compile do I have
to use with my HCS II?
You should always use the version of
that matches your ROM version. Although there's no way (yet) to determine the
ROM version from remote, the HCS II is smart enough to know the difference,
and will reject a mis-match on a program upload attempt.
What versions of ROM software is available for all the hardware?
The best place to view all versions of software is here
What is WinHCS?
WinHCS was written by Philippe C. Printz and is a Windows GUI front-end
Host. It can act as a wrapper for the DOS-based
compile to build and then upload a new
file. It currently supports up to version 3.63 of the HCS II ROM. The
intended operating system appears to be limited to Windows 95 and 98.
Windows XP virtualizes hardware, and requires that software needing to access
hardware like serial ports go through an API instead. There have been
unconfirmed reports that WinHCS does work under Windows XP otherwise, but
really the only way is to try it and find out.
When trying to reconfigure the AnswerMAN via its serial port, I get syntax errors and scrolling text or scrolling prompts. What's wrong? Also my keypresses are being ignored.
There are two things wrong:
Of course you did jumper the AnswerMAN's CFG pin to tell it to enter config mode....
What is XPRESS?
XPRESS is a production rule style language. In other words, it uses what's called event equations. So, if an event (an input of any sort, like heat, temperature, door, water, etc. sensors) get triggered, then an action (siren, log note, printer note, LCD display update, etc.) is taken. It is this language that allows the HCS II user to determine how their home is run.
Got any sample HCS XPRESS programs?
Have a look at the samples directory for a few good examples of a some real-world programs. Also many HCS II articles in Circuit Cellar Ink have snippets of XPRESS examples.
How big of an XPRESS program can I have on the HCS II SC?
According to Ken Davidson:
Maximum program size is about 18K based on the size of EVENTS.BIN. Compared to the number of systems we have out there (thousands), very few people have bumped into that size limit. The best way to keep your program from becoming too big is to limit the amount of text you use with LCD displays and the voice board. Normal XPRESS statements take up very little space. Raw ASCII text can't be compressed, though, so takes up a lot of space. The two statements you cite compile to exactly the same code. The Define statement is a compiler feature that makes your life easier. It doesn't result is any extra code generation. Also, the number of statements per line makes no difference. A carriage return character is treated the same as a space or a semicolon. You could put your entire program on a single line and the compiler wouldn't care (well, with some exceptions; code size still isn't affected, though).
The Edge state really isn't needed when you use If statements. An "If Input=On" is the same as "IfA Input=ON and Input=Edge" since they both allow the Then portion to be executed just once upon a transition of the input from Off to On. Of course, if what you're looking for is any transition of the input (either Off to On or On to Off), then the Edge state saves a bit of room.
How do I get accurate minute timers?
Use second timers, since they can count in the thousands of seconds. This is particularly useful for timers that need to run less than one hour.
How much log memory is available?
The HCS II has 32K of log memory available, which is not battery backed. This can easily be fixed by using a Dallas Semiconductor SmartSocket.
Are there version compatibility issues amongst different ROM versions?
Version 3.0 and up of the HCS II ROM has a different set of commands for selecting which SC to use. In the case of the 2.x ROM and below, these versions were explicit in choosing configurations based around the BCC180 and certain combinations of BCC bus boards. As of 3.0, the ROM probes the hardware to figure out what hardware is actually present in a BCC180-based HCS II. In short, a review of your XPRESS code is always a good practice to follow as you upgrade.
Additionally, version 3.0 and up uses the control lines of the serial port, whereas previous versions did not. Make sure that the cable used to connect the HCS II has all the conductors connected just in case.
Did Circuit Cellar ever produce an RS-485 repeater?
They did indeed. However the code hasn't ever been found (most likely due to it being a Micromint product).
How can I connect the HCS II to the Internet? Ethernet? LAN?
Really these are all asking the same question: How to Ethernet-enable the HCS II? As yet, no solution from either Micromint or Circuit Cellar has been released and it's not known whether they will. On the other hand, Mike Baptiste back in November of 2000 made an announcement that he had a working (but non-secure) prototype based around the TINI board.
Other users have used various serial to ethernet solutions over the years to varying degrees of success.
A number of commercial products have been released over the years that allows a serial port to pass-through a device that converts the serial communications into an ethernet-ready appliance. Such devices will usually take the serial data and permit transmission and reception via a user-selectable TCP or UDP socket.
At that point, it's really just a matter of writing a software client that will connect to an IP address and designated port number and start listening to the HCS II push out its serial data stream.
My BCC180-based HCS II sometimes won't respond to Host!
A BCC180 can appear to hang if the
Host doesn't get responses
to your commands (new program load, set time, etc.). This can happen
if a network module times-out because it is down or unavailable. When the
module does time-out, an 'E' appears in the Network modules window, but
has the side affect of not only shutting down the RS-485 network, but also
the console port! So far, this bug appears in v3.00 and up.
I have a 3.x or older ROM version of the HCS using an RTC180. Can this be upgraded?
Yes, it can. The upgrade as presented by Mike Baptiste at his website will work, simply by swapping out the RAM chips for faster versions and swapping the 74LS245s for 74HCT245s. (Of course you need to swap out the HD64180/Z80180/Z180 for the Z80S180 CPU.)
Then, you just need a version 4.x or newer HCS ROM,
At one point, by following the link, you could have purchased the whole upgrade kit.
Does any of this work in 50Hz electrical systems?
The HCS II can operate with electricity running at 50Hz. The only thing to watch out for is the PL-Link. A different ROM needs to be used for PL-Links running at 50Hz. There's a specially baked ROM image for such systems located in the files area at the top of this page.
Can the SpectraSense 2000 be upgraded to a Z80S180 CPU?
Although the SpectraSense 2000 is essentially the same hardware as the HCS II components put together, this hasn't ever been tested. In theory, it should work.
Does the RBUF-Term schematic contain an error related to the power LED?
On page 20 of the RBUF-Term manual, the schematic is missing the power LED. The power LED is tied to pin 10 of the resister network SIP and ground.
Where can I get part X for my boards?
As time wears on, technology moves forward, leaving a trail of obsolete parts. These days (2009/07/20) parts are getting harder and harder to source. Here are some parts for singled-out for consideration:
Otherwise, many of the parts in the COMM-Link boards as well as the HCS II are still readily available.