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Thread: Imsai FIF FDC project

  1. #1

    Default Imsai FIF FDC project

    I recently acquired another set of Imsai Calcomp drives and a two board set of an FIF FDC consisting of the FIB and IFM cards as well as all necessary cabling - between the cards, card to rear panel and a ribbon cable from the back of the Imsai to the drive enclosure. I spent a good part of today enhancing my Imsai 8080 page with resources manuals and a couple more images. Trying to gather as much information in one spot.

    I call this "The Money Shot" as in way too much money spent on old timey computers I really wanted that FIF set though.

    Imsai Full Stack.jpg

    Hamlin 7521d Solid State Relay

    Hamlin 7521D Electronic Relay.jpg

    I opened up the FDD cabinet and noticed this relay. It's obviously added by a user, I'm wondering if anyone might have an idea why? My guess was to control it remotely perhaps from the computer? Like a tape drive control on a Sol-20... Note the ends of the brown and tan wires on the VDC side. I don't like that they apparently swapped HOT and Neutral between the power cord and power supplies. I'm going to bypass it but I'm curious.
    ---
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  2. #2
    Join Date
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    Default

    I wouldn't be surprised if the relay is to cut out the spindle motors on the 8" drives. I've got a set of RX02 drives modified with just a mechanical switch to cut out the spindle motors on one or both drives. Presumably someone was worried about having a disk spun up for hours when there was no actual data access happening. Presumably your Calcomp drives have head load solenoids so it wouldn't be as bad as leaving, say, 5.25" drives with no head load solenoids running long-term, but perhaps there's added wear on the disk from just spinning in the jacket.

  3. #3
    Join Date
    Jan 2007
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    Yes, the Calcomp drives used in the IMSAI box have head-load solenoids. Not my favorite drives by a long shot--one nasty is that the DC power is on the same 40 pin connector as the signal lines. Stick the connector in "backwards" and you have (a) melted ribbon cable or (b) blown power supply fuse. In comparison to the Shugart SA800, the drives always felt a little chintzy.

  4. #4

    Default Blam goes the tantalum

    Blam goes the Tantalum C21 on the IFM Rev 6 board. I don't have any schematics for the IFM or the FIB boards. Has anyone seen schematics for these boards?

    C21 goes from ground to the input of a 7812. of the three or four capacitors there I can read they say 33 25v. I see a .1uf on the input of a 7812 on the MPU-A board. I probably should change them all. Suggestions for value?

    IFM blown capacitor.jpg
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

  5. #5

    Default Ifm p0 p1

    Quote Originally Posted by glitch View Post
    I wouldn't be surprised if the relay is to cut out the spindle motors on the 8" drives.
    The relay is on the entire primary to the power supply.

    Check this out on the IFM board I found a place where those relay wires must have gone.

    IFM P0 P1.jpg
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

  6. #6

    Default SIO Configuration

    Quote Originally Posted by jhalbrecht View Post
    I recently acquired another set of Imsai Calcomp drives and a two board set of an FIF FDC...
    To recap. I'm attempting to restore this Imsai with Calcomp drives to functionality. The Imsai 8080 and Imsai FDDs look to have been a working set. All the cards had necessary internal and external cables.

    I'm working on the SIO now. I'm going to need a console. I'd like to document it's original, or as received, configuration. I've saved images of all the cards as received here.

    I'm hoping someone comfortable with the SIO jumper settings can verify how the SIO is currently configured. I've read the manual a couple times. It looks to me like it's configured as RS-232 on I/O port 0 at 1200 baud on the left side edge connector. Looks like the other edge connector baud rate is not set. Eventually I'd like to verify this as console setup or reconfigure as such.

    SIO Rev 3 Front.jpg High resolution image of this SIO here

    I'm not positive about location A3 pins 7,8,9 and 10. Is that just choosing DCE / DTE? My SIO has A3 pin 7-9 and 8-10 crossed, the example jumpers have them straight 7-10 and 8-9

    Imsai SIO Suggested Settings.jpg

    I fired up the Z80 SBC I built and ran "Survey" with and without the SIO in the system. It's indicating to me that the SIO is configured at base port 0. Note the DDT run where I IN through the ports and get some data back on a couple of the ports,.

    ImsaiSioPorts.jpg

    I found a little monitor program by John Garza in hist files section (Check out hist pictures directory, some cool shots of his bench(s)) I pulled some code to create a little test. Othere monitors and Imsai documents appear to be pointing to base port 0 for a likely console location Base+2 I'm running this code in the Imsai 8080 with the 8080 cpu and Martin's 88-2SIOJP - I'm not doing testing, other than running 'Survey' in the SBC.



    Code:
                    ; jsio.asm jha 8/2/2018 testing sio
                    ; https://wiki.theretrowagon.com/wiki/Imsai_8080
                    ; from a Monitor program code by John Garza 
                    ; http://jgarza.sdf.org/files/M72.ASM
                    
                    ;------------------
                    ;IMSAI 8080 EQUATES
                    
     00FF =         LEDS	equ	0FFh	;IMSAI front panel output LEDs (top left)
     00FF =         SWCH	equ	0FFh	;IMSAI front panel input switches (left)
     0003 =         TTS     equ     03h     ;SIO channel A command port
     0002 =         TTI     equ     02h     ;SIO channel A data port (yes input=output)
     0002 =         TTO     equ     02h     ;SIO channel A data port
     0002 =         TTYDA   equ     02h     ;tty data available (ready to receive?) 
     0001 =         TTYTR   equ     01h     ;tty terminal ready (ready to transmit?)
                    
                    ;------------------
                    ;ASCII characters used
                    
     0000 =         NUL				EQU		0		; NULL (ZERO)
     000D =         CR				EQU		0DH		; Carriage return
     000A =         LF				EQU		0AH		; Line feed
     0008 =         CTRH            EQU     8       ; Ctl H Backspace
     007F =         DEL             EQU     127     ; Delete char
     0009 =         TAB             EQU     9       ; Tab char
     0018 =         CTRX            EQU     24      ; Ctl X Cancel
     0013 =         CTRS            EQU     19      ; Ctl S Suspend
     0011 =         CTRQ            EQU     17      ; Ctl Q Resume
     00F7 =         APOS            EQU     (39-'0') AND 0FFH  ;apostrophe
                    
     0100               org 0100h
                    jcot:               ; loop printing '7'
     0100 DB03          in TTS
     0102 E601          ani TTYTR
     0104 CA0001        jz jcot
     0107 3E25          mvi a,37        ; ASCII 7
     0109 D302          out TTO         ; Try to print to serial terminal
     010B C30001        jmp jcot
     010E               end
    This code loops in jcot: and the jz cot never making it to pc 107. I also tried just writing to port 2 without the status test. Nope.

    Does anyone have a know working SIO as a RS-232 device at base port 0? Can you comment and/or share an image of your configuration?

    Thanks, - Jeff
    Last edited by jhalbrecht; August 4th, 2018 at 09:59 AM. Reason: Add DDT IN port ...
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

  7. #7

    Default Helpful VCF thread

    This VCF Forum thread is helpful particularly if you log in so the images display. How to get output from SIO with Intel 8251A USART
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

  8. #8

    Default SIO Success

    It works! Success.

    This code works for me. It echos the keyboard to the screen. I configured the A3 jumpers as in the Imsai documentation. The trick was the software initialization. Now where is channel 1? BASE port + x? I better configure and test it too.

    Code:
    ; jsio.asm jha 8/2/2018 testing sio
    ; https://wiki.theretrowagon.com/wiki/Imsai_8080
    ; Originally from a Monitor program code by John Garza hence the EQUates
    ; http://jgarza.sdf.org/files/M72.ASM
    ;
    ; Important init code from VCF forums
    ; handy VCF threads for configuration
    ; http://www.vcfed.org/forum/showthread.php?64964-Imsai-FIF-FDC-project
    ; http://www.vcfed.org/forum/showthread.php?37137-How-to-get-output-from-SIO-with-Intel-8251A-USART
    ; 
    
    ;------------------
    ;IMSAI 8080 EQUATES
    
    LEDS	equ	0FFh	;IMSAI front panel output LEDs (top left)
    SWCH	equ	0FFh	;IMSAI front panel input switches (left)
    TTS     equ     03h     ;SIO channel A command port
    TTI     equ     02h     ;SIO channel A data port (yes input=output)
    TTO     equ     02h     ;SIO channel A data port
    TTYDA   equ     02h     ;tty data available (ready to receive?) 
    TTYTR   equ     01h     ;tty terminal ready (ready to transmit?)
    
        org 0100h
    init:
        mvi a,0    
        out TTS
        out TTS
        out TTS
        mvi a,040h
        out TTS
        mvi a,04eh  ; 8,1,n
        out TTS
        mvi a,037h
        out TTS
    
    inout:               ; loop read from serial, write it to serial. Serial terminal echo.
        in TTS
        ani TTYDA        ; DATA available?
        jz inout
    io1:
        in TTS
    ani TTYTR           ; ready to receive?
        jz io1
        in TTO          ; read character
        out TTO         ; write
        jmp inout       ; repeat
        end
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

  9. #9

    Default A3 works both ways

    Quote Originally Posted by jhalbrecht View Post
    It works! Success.

    This code works for me. It echos the keyboard to the screen. I configured the A3 jumpers as in the Imsai documentation. The trick was the software initialization. Now where is channel 1? BASE port + x? I better configure and test it too.
    I tried it with the A3 jumper in both configurations, it works both way. They change DTR and DSR and may be more important if I try some XMODEM... or need handshaking for a printer or modem...
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

  10. #10

    Default Channel B equates

    Quote Originally Posted by jhalbrecht View Post

    Now where is channel 1? BASE port + x? I better configure and test it too.
    I found the equate for the second channel, channel B (on the right hand side) just add 2. I put both channel equates in the test code. Comment out the one you're not testing.
    Code:
    ; jsio.asm jha 8/2/2018 testing sio
    ; https://wiki.theretrowagon.com/wiki/Imsai_8080
    ; Originally from a Monitor program code by John Garza hence the EQUates
    ; http://jgarza.sdf.org/files/M72.ASM
    ;
    ; Important init code from VCF forums
    ; handy VCF threads for configuration
    ; http://www.vcfed.org/forum/showthread.php?64964-Imsai-FIF-FDC-project
    ; http://www.vcfed.org/forum/showthread.php?37137-How-to-get-output-from-SIO-with-Intel-8251A-USART
    ; 
    ; works with straight through cable
    ;
    
    ;------------------
    ;IMSAI 8080 EQUATES
    
    LEDS	equ	0FFh	;IMSAI front panel output LEDs (top left)
    SWCH	equ	0FFh	;IMSAI front panel input switches (left)
    
    ; channel a
    ;TTS     equ     03h     ;SIO channel A command port
    ;TTI     equ     02h     ;SIO channel A data port (yes input=output)
    ;TTO     equ     02h     ;SIO channel A data port
    
    ; channel b
    TTS     equ     05h     ;SIO channel B command port
    TTI     equ     04h     ;SIO channel B data port (yes input=output)
    TTO     equ     04h     ;SIO channel B data port
    
    TTYDA   equ     02h     ;tty data available (ready to receive?) 
    TTYTR   equ     01h     ;tty terminal ready (ready to transmit?)
    
        org 0100h
    init:
        mvi a,0    
        out TTS
        out TTS
        out TTS
        mvi a,040h
        out TTS
        mvi a,04eh  ; 8,1,n
        out TTS
        mvi a,037h
        out TTS
    
    inout:               ; loop read from serial, write it to serial. Serial terminal echo.
        in TTS
        ani TTYDA        ; DATA available?
        jz inout
    io1:
        in TTS
    ani TTYTR           ; ready to receive?
        jz io1
        in TTO          ; read character
        out TTO         ; write
        jmp inout       ; repeat
        end
    ---
    KF7CRU @jhalbrecht @TheRetroWagon Looking for Solid State Music SB1 please DM me.
    http://www.theretrowagon.com/vcf-west-2017/

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