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Thread: RX and TX ready mask ??

  1. #1

    Default RX and TX ready mask ??


    Now, my Imsai 8080 is running on the terminal. I wrote a few small routines to send some stuff to terminal and reverse. I want to burn a machine language monitor to eprom and i have to change some parameters. I use interfacer 1 serial card. My dataport is 00, my statusport is 01. But what is the rx rdy mask and tx rdy mask ?? I cannot find anything in the interfacer manual ! Please help !



  2. #2


    From the manual, page 4 Status Port, Transmiter Empty is bit 0 and Data Available is bit 1 of the SWEA port. RX rdy would be 02H and TX rdy would be 01H. There are several error bits that one might want to clear before looking at the receive bits.

  3. #3


    Thank you ! i have read the manual. my card setup is data port at 00 and status port at 01. how can tx rdy be port 01 ? there is status port. How did you know that rx rdy is port 02 ? can you explain how to know this ?

    thank you very much !


  4. #4


    Not port 2 bit, mask value 02H.
    Both bit mask on port 1. You asked for the mask, not the port.

    page 8A-3
    pin 19

    Last edited by Dwight Elvey; October 18th, 2019 at 04:53 PM.

  5. #5


    Additional to what Dwight pointed out above...

    The purpose of each of the 8 bits that you can read from the Interfacer 1 status port (which you have configured to be input port 01H) are defined on page 4 of the Interfacer 1 manual:

    Data bit 0 provides status of "transmitter buffer empty" (UART pin 22)
    Data bit 1 provides status of "data available" (UART pin 19)
    Data bit 3 provides status of "parity error" (UART pin 13)
    Data bit 4 provides status of "overrun" (UART pin 15)
    Data bit 5 provides status of "frame error" (UART pin 14)

    Page 11 in the Interfacer 1 manual provides a nice example (in 8080 assembly language) of how to use a "data bit" mask to determine the status of a specific "data bit" within the byte of data that is read from the Interfacer 1 status port.


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