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THROUGH THE LOOKING GLASS

Taking a Look at the PIC18Cxxx Series
by David Brobst

Start ý PIC18Cxxx Chips ý Memory ý Data Memory ý Advanced Indirect Addressing ý Deep and Accessible Stack ý Interrupts ý Power-On Features ý Clock Speed ý 10-Bit A/D ý Hardware Multiplier ý Timers ý CCP/PWM ý USART ý I²C Master ý Table Read/Write ý Current Status ý Sources and PDF

HARDWARE MULTIPLIER

The PIC18Cxxx has an onboard hardware, 8 ý 8, unsigned, multiplying circuit. The multiplier takes only one instruction cycle to perform the multiplication. Although not a 32-bit MAC unit in a DSP, this hardware multiplier can significantly speed up the response time of the controller to outside stimulus. Table 3 states the comparison between firmware-implemented multiplication and the hardware implementation of the PIC18Cxxx family.

Table 3ýThe hardware multiplier on the 18Cxxx family can greatly speed up math-intensive operations.

As can be seen in Table 3, a 16 ý 16 signed multiply implemented with the 8 ý 8 hardware multiplier enjoys about a seven-times speed increase over the firmware implemented version. In many embedded systems, there can be many multiplies per loop, so the speed variation can make the difference between getting the job done and failing.

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