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
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