Blinkenlights (not only for PDP-11) -- the sequel

Hello all! I have been busy interfacing the "real console" to SIMH last week. During last week Vince has drawn some Printed Circuit Boards (PCBs). Vince and I had frequent e-mail contact working through the designs. Basically, this e-mail is an inquiry to which extend people would like to embark on this project. So, let me know if you would like to participate in this project!! But before you put the $$ on the table I will try to explain in more detail what the status of my project is and what use it can have ... In this e-mail I address the following topics: 1. Some ideas where this project can be used. 2. A small description of the hardware. 3. An introduction to the firmware. 4. The interfacing to SIMH, state of affairs. 5. An estimate on the building costs. 6. What the project participants can expect. Allthough my primary design goal was a "blinkenlight" console based on the PDP-11 and a PC running SIMH, the hardware is multi-functional with the large amount of digital inputs and outputs. You can think of several other applications to control with this harware, for example a robot arm with some stepper motors ... just use your imagination! During this weekend I will update my website with a few .mpg files to show you a console in operation with SIMH, and a few samples of the console running in stand-alone mode. So, check next Monday the site http://www.pdp-11.nl/ and click on the link "homebrew PDP-11" in the left pane. The latest software version will also be downloadable. ** 1 ** Ideas for use. First, let me say that I do NOT support the idea of trashing a nicely working real PDP-11 computer to get a console! If you have a real PDP-11 console, this project will allow you to use the computer that runs SIMH (PC) to be controlled with the PDP-11 console as the real thing! This hardware is an other option for people that do not have a real PDP-11 with blinkenlight console or do not have the space for such a big (UNIBUS) machine. A third option for usage of this hardware is for people that *have* a real PDP-11, but running that system is noticed on the electrical bill! One could build a PC inside the real PDP-11, and disconnect the flat cables from the real console and connect them to this hardware. Running the PC/SIMH with the real console looks like the REAL THING but without the big energy consumption. Of course, the real disks and other peripherals are all "inside" the PC ... This setup might be a solution for a museum. The system is exhibited in a running state, and the changes made can simply be reverted to the original state. The fourth usage is for other computers that have a blinkenlight console, and are emulated by SIMH. The PDP-11 file in SIMH shows how to interface your favorite machine. You can run your favorite vintage computer in SIMH with that sexy switches and light console! ** 2 ** The hardware. We have two different design approaches. The first is called the "combi-board". The combi-board is a single PCB which contains the CPU etc. and *eight* 8-bit output ports and *six* 8-bit input ports. This in/out configuration can support the largest PDP-11 console, viz. PDP-11/70 full console! The second design consists of *two* PCBs, one is called the Core Board, the other the I/O Board. The Core board holds the CPU, etc. and the I/O Board offers also 8 8-bit output and 6 8-bit input. The combi-board is a little cheaper, but the two-PCB design offers expandability if you need more outputs/inputs. (who said this hardware design is for console interfacing only ?!) The design efforts of Vince and I are focussed on the 2 PCB version. Note. If you checked my website and had a look at the schematic diagrams, I must tell you that there are a few minor changes. For example, the expensive Dallas RS-232 converter chip is replaced by the cheaper MAXIM MAX232A chip. Further the 8kbytes firmware EPROM 2764 was full up till the last 500 bytes, so there was little room for any future development. The address decoder LS138 is substituted by one 74LS139 thus enabling the change from the 2764 to one 27128 16 kbytes EPROM. That also eliminates the need for an optional 2nd 2764 EPROM socket, which saves space on the PCB. ** 3 ** The firmware. The firmware contains in approx. 8 kbytes a simple debugging monitor and the console software. Which software (monitor or console) starts is determined by a push-button at reset. Both talk to a terminal via the RS-232 port at 9600 Bd. In the console mode, the RS-232 connects to the interface software added to SIMH to control the console from SIMH. It is completely free to which input port and bit(s) you connect the switches and the (momentary) toggles. Via the firmware you 'learn' the console where the switches/toggles are connected. The firmware handles the appropriate way of processing toggles and debouncing. ** 4 ** Interfacing to SIMH. I added two extra files (one .c and .h), and made simple changes and additions to the files scp.c and pdp11_cpu.c of the SIMH software. Current state of affairs: ADDRESS and DATA LEDs are functional, also the USER, VIRTUAL, CONS, and RUN LEDs. I have not yet spend time to find a way to implement the control from SIMH for the BUS & PROC LED. The toggles LOAD ADRS, EXAM, CONT, START, and DEP work as you would expect on a real PDP-11/40 (aka PDP-11/35 OEM version). The ENAB/HALT switch is operational too, HALTs the emulated software when it runs, and changes CONT and START to STEP and RESET while in the halted state, the switch in the position HALT. While STEPping the software the ADDRESS & DATA LEDs are correctly updated after every single instruction execution. ** 5 ** The costs of the project. First, I need to know how many people would like to participate in this project. The more people join, the cheaper the production costs of professionally made PCBs become. The (single) combi-board will be somewhere around $40 to $50, and the two PCB design (Core and I/O) will be slightly more expensive, the 2 boards will cost approx $10 more than the combi-board. This solution provides expandability for hobbyists, or use in other projects. The required components to populate the PCB(s) can be seen in the diagrams on my website. You can make an approximate calculation what these components cost. Probably prices are lower in the USA compared to The Netherlands where I live ... ** 6 ** What will you get if you join the project? I will write a clear, well documented manual that describes the PCBs, the protocol, and a step-by-step DIY building the PCB(s) with clear *full color* pictures. The firmware and the modified SIMH files can be downloaded from my website. However, I will offer a pre-programmed 27128 for just the cost of the IC (here in The Netherlands). You can also snail-mail me an *empty* 27128, and I will program that one for you, but I doubt if that option would be cheaper ... REMARK. If you would like to participate in this project, but are not sure to successfully solder the PCB(s), I will offer a (payed) service that delivers a working/tested PCB (or two PCBs). The modifications required in SIMH are done for version 3.2.0. The first work was done on version 2.4.0, and I found a few changes were needed, as scp.c was changed. However, when a new version of SIMH is available I will put the required changes on my website within, say two weeks. So, unless SIMH changes drastically, continuity will be guaranteed on short notice, else I will need a little more time! If you join the project for the hardware, but do not intend to use it for a console, but in some other project, you can ask me questions too. I will give answers to the best I can as long as they involve the design, or the software. I have good knowledge of MC6802 assembly programming. Please feel free to write an e-mail to me if you have any questions! I will try to answer all questions in private e-mail, next week. If the question is general I will post a follow-up in this thread. regards, - Henk, PA8PDP.