Depends on the length of the bus, load, impedance, frequency, technology (TTL, CMOS, open-collector, open-drain, tri-state), single ended, differential, etc.From time to time I see resistor networks used as pull-ups on buses (address, data), and am wondering if there is a recommendation as to where along the bus they should be physically placed.
There is an additional reason for using them unrelated to where they are located. This occurs in a system with multiple bus controllers, for example a CPU and a DMA controller. The pullups enforce a deterministic bus state when either controller relinquishes the bus followed by some delay before the other controller acquires the bus. This prevents uncontrolled transitions on the bus during the delay.From time to time I see resistor networks used as pull-ups on buses (address, data), and am wondering if there is a recommendation as to where along the bus they should be physically placed.
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by Jake Hertz
by Jake Hertz