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I have a query concerning the correct way to represent a boolean = expression involving active low logic signals.
The expression in question is for a simple address decoder for an 8-bit = processor with a 16-bit address bus interfaced to a 32K byte ROM decoded = between locations 0000-7FFF. The ROM has an active low chip enable = input, /CE. For the purposes of this discussion I assume that an active = low read signal /RD from the processor must be included in the decoding = (I appreciate that most ROMs have a separate /OE and that /RD could be = connected to /OE).
The logic circuit is (I think!) obvious; we need a logic zero on /CE = when both A15 and /RD have a logic zero on them, so a 2-input OR gate is = required with A15 and /RD as inputs and the output connected to the = ROM's chip enable /CE input.
ASCII art diagram, mono-spaced font such as courier required
__ ___ __ RD