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C251: HOW FAST IS THE 251?

QUESTION

How fast is the 251?

ANSWER

The 8051 divides the external oscillator by 12 to get the instruction clock. Therefore, a 12MHz oscillator generates an instruction clock of 1MHz. The 8051 executes instructions in units of instruction clocks.

The 251 divides the external oscillator by 2 to get the state cycle. Therefore, a 12MHz oscillator generates a state cycle clock of 6MHz. The 251 executes instructions in units of state cycles.

Considering these figures, you should see a 6× performance boost when you use the 251. However, this accounts for identical instruction timings among the 8051 and 251. If you also compile your code in 251 source mode, you will see an even greater performance increase.

Last Reviewed: Monday, June 7, 2004


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