Microprocessor
While using a frequency counter for measuring frequency, two modes of measurement are possible: Period time Frequency mode There is a ‘cross-over frequency’ below which the period mode is preferred. Assuming the crystal oscillator frequency to be 4MHz, the crossover frequency is given by

 2 Mhz.
 8 Mhz.
 2 Khz.
 1Khz.

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Microprocessor
Cycle stealing mode of DMA operation involves

 DMA controller taking over the address, data and control buses while a block of data is transferred between memory and I/O device
 The DMA control waiting for the microprocessor to finish execution of the program and then takes over the buses
 While the microprocessor is executing a program an interface circuit takes over control of address, data, control buses when not in use by microprocessor
 Data transfer takes place between the I/O device and memory during every alternate clock cycle

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Microprocessor
Which of the following is not true during the execution of an interrupt service routine, which does not contain any EI instructions

 all interrupts except non-maskable interrupt are disabled
 the microprocessor cannot be interrupted by any mask able interrupt
 the microprocessor cannot be interrupted by any interrupt
 the microprocessor can be interrupted by a non-mask able interrupt

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Microprocessor
A good assembly language programmer should use general purpose registers rather than memory in maximum possible ways for data processing. This is because:

 Of limited set of instructions for data processing with memory
 Data processing with registers is easier than with memory
 Data processing with registers takes fewer cycles than that with memory
 Data processing with memory requires more instructions in the program than that with registers

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