during data and program memory access. PMXEN enables the extended external memory (IC14) during external program memory access. The memory decoder design supports paged operation, in this unpaged application, the unused inputs are tied low through a 10 kW resistor (highlighted!), R314, and unused outputs are tied high through 10 kW pull-up resistors R316..320. IC16 is a Programmable Logic Array (PLA), known as the bridge controller, which provides a
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