8085 microprocessor logical instructions won't affect the carry flag, right?

Sanjaykmr852

Sanjaykmr852

@sanjaykmr852-CLqw5Q • Oct 26, 2024
I read that logical instructions won't affect the carry flag.if so XRA A can clear the carry or not?
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  • pratap singh, upendra

    pratap singh, upendra

    @pratap-singh-6xlmve • Jul 20, 2015

    The answer depends upon the logical instruction you are using. For example, CMC does complement the carry flag despite being a logical instruction.

    The best way to find whether or not a logical instruction changes carry status is to implement it in a small program. Track the status of carry flag before and after the execution of the instruction.

    That is the only sure free method to study any instruction in 8085 microprocessor. No textbooks, no Internet.
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  • Sanjaykmr852

    Sanjaykmr852

    @sanjaykmr852-CLqw5Q • Jul 20, 2015

    Thanks..I studied 3 buses in 8085 like address bus,data bus,controlbus. But physically how many buses are connected with 8085?
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  • pratap singh, upendra

    pratap singh, upendra

    @pratap-singh-6xlmve • Jul 21, 2015

    Well, as per the convectional wisdom, the number of buses in 8085 is equal to number of electrical wires that you can spot. It is because technically speaking, a bus is a physical connection between two components and it is meant to transmit electrical signals between them.

    For the sake of simplicity and understanding, the less important connections (in context to programming) were excluded from being called as buses.
    • It is because, either way, you don't have to deal with them during your programming.
    • For example: - you do not need the wire's information connecting two decoders during your programming session. You assume that it is already connected.
    In context to programming, however, the buses are classified as data, control and address bus because we are interested in their state.

    To summarize:
    • any electrical connection = bus
    • a subset of connections that is relevant in context to programming is either a data, control or address bus.
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