Image Map Image Map
Page 5 of 5 FirstFirst 12345
Results 41 to 49 of 49

Thread: CIT-101 terminal

  1. #41
    Join Date
    Dec 2013
    Location
    Near Milwaukee Wisconsin
    Posts
    1,159

    Default

    Chuck, I think I played with the patch area in the past, but do not remember exactly how it worked. Maybe when I have more time or the need I'll attempt to figure it out again and see if it works.

    The last couple of weeks were so nice, weather wise, that I could not find my way into the basement to work on the C-ITOH monitor and keyboard. But this week the weather turned back toward winter, cold snow, rain wind, brrrrr! The basement seemed welcoming.

    I took some time to look at the circuit in the keyboard CB. It is different from what is shown in the DEC VT-100 maintenance manual. The VT-100 uses a 12 volt piggy back signal. The keyboard signal is on top of the monitor signal. Each has circuits to separate the two. The C-ITOH seems to just use a 5 volt signal with a mixture of the monitor and keyboard signals. There has to be a start up signal, probably to sync the monitor and keyboard time wise. Then when the system is waiting for the user to press a key, the monitor sends a 'start' word. This is a guess on my part. The keyboard then responds with (no user key pressed) an end of list or time out response. The monitor then sends another word, I'm guessing that this may be the status word that contains the LED status, the keyboard then responses with the same end of list or time out response. Then should the user press a key, the end of list marker after the monitor start word, is replaced with the ASCII code for the key. This is again followed by the status word. Let me said again, I'm guessing at this. When I have time I want to change what I think is the status word for the LED and see if what the monitor sends changes with the LED pattern.

    This is a picture of the keyboard response (top trace) and the combined monitor and keyboard signal (bottom trace).
    20190429_172253.jpg

    This is the circuitry I traced out on the keyboard CB and some thoughts on the waveforms seen above. Need to think about this some more and do some more testing, Mike.
    Signals1.jpg

  2. #42
    Join Date
    Dec 2013
    Location
    Near Milwaukee Wisconsin
    Posts
    1,159

    Default

    Over the last couple of days I wrote a short program on the PDP8E that will flash the C-IOTH LED's. This test program will allow me to connect up the logic analyzer to see how the monitor sends this kind of information to the keyboard. I wrote the program using the C-IOTH keyboard and monitor. This is another key layout that is a little different than all the others, but I'll get used to it. Using the keyboard I found a couple more keys that stick on occasion and produce double letters. Later I will pull those and replace them. I'm still hoping that I can get some new switches. I did have a problem with lighting #3 LED. At first I thought that the keyboard had a problem, but turned out it was my program, should have known. Anyway, the LED flash one at a time in sequence. And an added benefit of using 110 baud, I do not have to have a time delay in my program. The slow serial speed causes the flash rate to be just under 1/2 second. Maybe next week I will open up the key board and re connect the logic analyzer and see how these signals are sent. Thanks Mike

  3. #43
    Join Date
    Mar 2006
    Location
    Salt Lake City, UT, USA
    Posts
    245

    Default

    Quote Originally Posted by Mike_Z View Post
    Using the keyboard I found a couple more keys that stick on occasion and produce double letters. Later I will pull those and replace them.
    By "pull those and replace them" are you just referring to the keycaps? The switches probably just need a little cleaning. Try some isopropyl alcohol and if that isn't enough, maybe a little bit of deoxit.

  4. #44

    Default

    It's nice to see everything's hanging together nicely!
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  5. #45
    Join Date
    Dec 2013
    Location
    Near Milwaukee Wisconsin
    Posts
    1,159

    Default

    These switches are difficult to get anything into them. But... they come apart easily, by loosen up a couple tabs. I did repair two this way and one was toast. So I'll try to repair them, but we will see.

    Witchy, these keyboards turned out to be pretty good. I'm confident that I'll one that will work just fine. AND maybe a good backup. Thanks
    Mike

  6. #46
    Join Date
    Dec 2013
    Location
    Near Milwaukee Wisconsin
    Posts
    1,159

    Default

    This morning, I started up the PDP8E, the logic analyzer and the C_IOTH terminal. I stretched out sample rate so that I could get 2 or 3 seconds of waveform on the LA. Again I connected up to see the output of the Keyboard from the 8048 and the composite signal on the Comm. line. The comm. line has both the monitor and the keyboard signals on it. I can easily separate the two signals by sight. I wonder whether or not my Logic analyzer can do any math. Like add two signals to make a third. Then I could subtract out the keyboard from the composite and see just the monitor signals. Suppose I'll have to break out the manual. It's an HP 16700. After starting the test program, which resets all the LED's, lights #1, resets, lights #2, resets, lights #3, resets, lights #4, and then loops; the LA was started and a boat load of data was recorded.
    The monitor seems to send out signal that must act a start for the keyboard. It is sent every other cycle and the keyboard responds after about a milliSec. If the keyboard responds with a 200 octal, no key was pressed. The monitor then sends the status word. I'm assuming that the status word is similar to the VT 100 word. The monitor seems to repeat start, then status over and over. If the user pressed a key, the 200 octal is replaced with the ASCII keycode for that key. It is easy to see that monitor sends the same status word over and over until it is changed. I had some trouble with the format of the keyboard communication, but found that it starts with one start bit (the bits are about 210 uSec each), then the 8 bit data word, LSB first, and finishes up with two stop bits. The monitor start word seems to be 132 Octal. I had earlier said it was something else, but that is when I was in error about how the data was being sent. No keys are pressed in this test, so the keyboard responds with 200 Octal, every time. The monitor then send the status word. After the monitor receives the all LED off escape sequence from the PDP8E, the status word was 373 Octal. This status word persisted until the PDP8E sent the LED #1 on code. Then the status word was 173 Octal, LED #2 on caused 273 Octal, LED #3 on caused 333 Octal and LED #4 on caused 353 Octal. Comparing this to the DEC VT-100 status word I was confused, until I remembered that D0 in DEC is the MSB not LSB. So this is what I learned about the C-ITOH status word

    MSB LSB
    11 111 011 All LED off
    01 111 011 LED #1 on
    10 111 011 LED #2 on
    11 011 011 LED #3 on
    11 101 011 LED #4 on

    The zeros, lows corresponds to the LED that is on. This is the same the DEC VT-100 status word. Assuming the other bits are the same. D5 must be the on/off line bit. Zero being on line. D4 would be Keyboard locked, D6 start keyboard scan, D7 speaker click.
    I read about Keyboard locked. This seems that if the terminal buffer is full the terminal will lock the keyboard or in the case of the VT-100 if XOFF is sent the keyboard is also locked. I could not find the XOFF information in the C-IOTH manual. I do not think that the C-ITOH needs the D6 for scanning the keyboard, since I do not think this keyboard is scanned like the VT-100. So maybe it is not used or maybe for some other purpose.

    My next test program will be to click the speaker for D7 and send XON/XOFF to see if that locks the keyboard. I think the other functions of the keyboard is to recognize the escape sequences, save or just send the RS232 interface parameters and do things like alternate character sets. Mike

  7. #47

    Default

    Witchy, these keyboards turned out to be pretty good. I'm confident that I'll one that will work just fine. AND maybe a good backup. Thanks


    No problem! It's excellent to see them go to a good home
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  8. #48
    Join Date
    Dec 2013
    Location
    Near Milwaukee Wisconsin
    Posts
    1,159

    Default

    Well..... I've been busy assembling Vince's new memory and boot board over the past week and have not had a chance to work on the C-IOTH keyboard. AND the weather is turning to Model T time. But, over the week end I wrote a beep program and started to look for the 'beep' signal in the monitor to keyboard signals. At first I could not find it. I had thought it was combined with the LED signals. Seems that the beep is a part of the first word sent to the keyboard. The C-ITOH keyboard does not seem to follow the VT-100 status word communications. The C-ITOH monitor seems to send two serial words to the keyboard over and over. In the picture,
    BeepX.jpg
    The first circle (On the left) is the data the monitor sends to the keyboard most of the time, after initialization. I suspect that maybe other setup data may also be in this word. Then the second word has information regarding the LED's. The second circle has the code for resetting all the LED's. The third circle is the 'beep' signal. It occurs only once, probably why I didn't see it, besides my looking at only the second word. You can see that the one pulse in the beginning of the word is missing. Zero's mean do something, one's not. So I'm thinking that I may try XON/XOFF next.

    Mike

  9. #49
    Join Date
    Dec 2013
    Location
    Near Milwaukee Wisconsin
    Posts
    1,159

    Default

    I wanted to test the keyboard Lock LED. I had thought that XON/XOFF would do this, but apparently not. I added XON/OFF to my PDP8E test program and watched for the Lock LED to light, but it did not. The C-ITOH User's manual says little about the LOCK. I read in the VT-100 book that the lock is a function of trans/rec buffer being full. SO I am not sure how to test the LOCK. I figure I move on and try to capture what happens during the Monitor Keyboard boot. Mike

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •