Spring 1979, Issue 2

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  1. The NMI ‘Break’ can only be used with NASBUG T4 and B-BUG. This should be made on a small piece of veroboard and mounted somewhere appropriate. To connect it, a wire should be run from pin 8 of IC42 (under the board)to the input of the circuit. The CPU should be lifted from the board and pin 17 carefully bent out horizontal, the CPU may then be replaced. The output of the circuit is connected to pin 17 of the CPU, using a ‘Soldercon’ pin. DO NOT SOLDER TO THE CPU.

    Fig 1. “Snow Plough”

    Fig 2. “NMI Break”


  1. Suppose you want to compare HL with DE, without changing the contents of either register.

    Try this:

    B7              OR A
    ED 52           SBC HL, DE
    19              ADD HL, DE

/ .. ..

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