scott@max.u.washington.edu (01/23/90)
Could any who is knowlegable about monitors tell me what is the difference between a TTL monochrome monitor and a Composite monochrome monitor? Is it merely a different in the connector type. It seems that TTL monitors have DB9 type connectors and a Composite monitors have RCA phone plugs. If the difference goes beyond difference in connector-type, how difficult is it to adopt a TTL monochrome monitor so that it will accept the signals that a Composite monochrome monitor would accept. Any comments would be appreciated... Scott K. Stephen
rkl@cbnewsh.ATT.COM (kevin.laux) (01/24/90)
In article <13120.25bb055b@max.u.washington.edu>, scott@max.u.washington.edu writes: | Could any who is knowlegable about monitors tell me what is the | difference between a TTL monochrome monitor and a Composite | monochrome monitor? Is it merely a different in the connector type. | It seems that TTL monitors have DB9 type connectors and a Composite | monitors have RCA phone plugs. Simply put, the TTL monitors have the components of the video signal such as horizontal and vertical sync on the individual pins of the DB9 connector. The Composite (Sync) monitors have a single pin that carries all the components of the video in a single signal. The monitors have different circuitry inside to handle the two types of input and one cannot handle the other type. (There *are* monitors that have multiple sets of input connectors and a switch to set where/what the input is.) | If the difference goes beyond difference in connector-type, how | difficult is it to adopt a TTL monochrome monitor so that it will | accept the signals that a Composite monochrome monitor would accept. You would need to get a converter that accepts Composite Sync and outputs it as TTL. |-rkl
dmt@pegasus.ATT.COM (Dave Tutelman) (01/25/90)
In article <13120.25bb055b@max.u.washington.edu> scott@max.u.washington.edu writes: >Could any who is knowlegable about monitors tell me what is the >difference between a TTL monochrome monitor and a Composite >monochrome monitor? Is it merely a different in the connector type. >...how difficult is it to adopt a TTL monochrome monitor so that it will >accept the signals that a Composite monochrome monitor would accept. I did the opposite conversion (TTL Hercules adapter to monochrome composite monitor) about six years ago. It was non-trivial. What you suggest is even harder. Here's what you'll have to do: 1. The sweep frequencies are different. You'll have to tweak the horizontal sweep circuit of the TTL monitor to run about 20% slower. 2. The Sweep pulses (hor & vert) are combined in with the composite signal. You'll need a sync separator circuit (look in your favorite TV circuit design handbook) to get them onto the separate leads required by TTL. 3. Similarly, the intensity information is combined in with the composite signal. Separating this out to the intensity line is NOT a standard TV circuit. However, if you understood the sync separator circuit really well, you could adapt the techniques to design an intensity separator circuit. 4. Finally, you'd need a little level-shifting/impedance-matching circuitry. Simple, and probably passive. When I did the opposite conversion, I had to solve #1 and #4, just as you will. #2 and #3 were much easier conversions (like a gate and a couple of resistors and diodes) than going from composite to TTL. You don't give a reason for wanting to do this. Here are a couple of possible reasons, and their "solutions": - You already have a TTL monitor and a CGA board, and you're cheap. (That's why I did my modifications six years ago.) There may be a display board that looks to the bus and program like a CGA, but puts out a TTL mono signal; I don't know. However, that's likely to be much more expensive than just buying a cheap mono-composite monitor or Hercules-clone board. - You want to run both CGA and MDA software on the same computer, into the same monitor (say, run games occasionally on a machine that's otherwise text-only). In this case, don't spend money on a second CGA board. Get a CGA-on-Hercules emulator (software) for your Herc board. There are a couple of shareware products out there that work on about 70% of the CGA software: SIMCGA and my HERCBIOS. - You MUST run both CGA and MDA software on the same monitor, and cost is not an object. Look into a (perhaps pricey) board/monitor combination that does this. I know they exist, though I couldn't give you a brand name off the top of my head. Dave +---------------------------------------------------------------+ | Dave Tutelman | | Physical - AT&T Bell Labs - Lincroft, NJ | | Logical - ...att!pegasus!dmt | | Audible - (201) 576 2194 | +---------------------------------------------------------------+
jdudeck@polyslo.CalPoly.EDU (John R. Dudeck) (01/25/90)
>| If the difference goes beyond difference in connector-type, how >| difficult is it to adopt a TTL monochrome monitor so that it will >| accept the signals that a Composite monochrome monitor would accept. > Why do you want to do this? Is it for a computer such as an old home- style TI 99/4A or Atari? If we are talking about systems previous to the VGA which is analog, most video cards have TTL outputs in addition to any composite video output that they may have. The problem comes with systems that have the older CGA type of RGB output, which many monochrome TTL monitors can't take. The R, G, and B outputs are on different pins of the connector from the monochrome video signal that the monitor expects. Some monochrome monitors will accept RGB and convert it to different shades of monochrome. For example, the Princeton MAX-12 does this, as does the Thomson 450A. If you have an EGA card, there should be an EGA monochrome output that is compatible with standard mono monitors. -- John Dudeck "You want to read the code closely..." jdudeck@Polyslo.CalPoly.Edu -- C. Staley, in OS course, teaching ESL: 62013975 Tel: 805-545-9549 Tanenbaum's MINIX operating system.
akcs.amparsonjr@vpnet.UUCP (Anthony M. Parson, Jr.) (02/02/90)
On an XT-clone, I have a monochrome ($49, new) monitor connected to an old Parasise Autoswitch EGA 480 board. Runs monochrome fine with the mono monitor, works fine with EGA and CGA monitors (which I used to use it with) Eventually, you will want color, so I suggest you look for a used board like this. Oh yes, the dox for the board state you can connect a mono monitor. Since the board is autosynching, all you need to do is turn on the monitor before you turn on the computer and it work okay. Only prob so far: if I use a screen blanker, such as the one that is part of Desqview, the display goes haywire when blanking occurs, and I have to reboot the machine; so don't use a screen blanker with this particular setup. Incidentally, Norton's Utilities correctly identifies the setup as an EGA card w/256K