80-Bus News

  

July–October 1982, Volume 1, Issue 3











Page 28 of 51











Handling the printer was the next problem, characters are output at 9600 baud, which is a lot faster than the printer can print them. The printer has a 1K buffer, but this is soon filled. Fortunately the printer is equipped with a handshake signal which may be connected to pin 2 of SK2, signalling when the buffer is full, or the printer is out of paper, etc. A simple piece of software supervises the printer. Before sending a character the following code is called:

        PUSH AF 3         ; Save the flags and the A register
BUSY    IN A,(0)          ; Get the input into the A register
        RLA 3             ; Move the bit to be tested into the C flag
        JR C, BUSY 3      ; Test and loop if busy
        POP AF

After which the software may direct the character to be sent to the printer.

This finishes my summary of the major changes I have made to my Nascom 1, I hope the above will be of help to someone, and that it will solve some of their problems.







Pins 3 & 13 of IC46 must be
connected to A12 & A11

MODIFICATIONS TO ALLOW THE USE OF 2K RAMS
AND EPROMS ON THE NASCOM 2.     JEFF ROLLASON 82












Page 28 of 51