Question

What two clocks are contained in the 6811 microprocessor?

Answer 1

Instructions takevarying numbers of machine cycles to eecute, depending on their complexity. The 6811 we're using operates at a frequency of 2 megaherts (Mhz.), meaning that it executes 2,000,000 machines cycles per second. The period of a machine cycle is then 0.5 microseconds, so an instruction that requires 3 machines cycleswill take 1.5 microseconds of real time to execute.

In general, longer instructions (those needing two, three, or four bytes) take longer (more machine cycles) to execute, although there are some exceptions to this rule.

A microprocessor does its work by moving data from memory into its internal registers, processing on it, and then copying it back into memory. These registers are like variables that the processor uses to do its computation. There are two different types of registers : Accumulator and Index registers.

Accumulators are used to perform most arithmetic operations, like addition, subtraction, or performing logical and bit operations (and, or, invert). Result of such operations often are placed back into a register.

Index registers are used to point at data that is located in memory.