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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

In the early ý90s, the venerable line of PIC16C5x products introduced a new way of thinking for 8-bit designs. Blazingly fast for its time, the PIC16C5x series was based on an EPROM one-time-programmable (OTP) program memory architecture. With its low-cost approach, small and medium quantity designs could benefit from the advantages of embedded intelligence.

The drawback to these first controllers was that they were bare bonesýno interrupts, limited stack and subroutine memory, a paucity of onboard peripherals, and limited program memory size. Later, a mid-range line of controllers was introduced, the PIC16Cxxx family.

This line of controllers included interrupts, a larger stack, more data memory, much larger program memory, and an abundance of peripherals (A/Ds, timers, USARTs, parallel ports, serial ports, EEPROM, flash memory, and more). Once again, these controllers were aggressively priced and available with short lead times and in reasonable quantities. The death knell of the masked-ROM-only applications had sounded, and other companies began to roll out lines of OTP controllers.

Next came the remarkable 8-pin microcontroller, the PIC12Cxxx family. These basic controllers were based on both the low-end and mid-range families and were priced under $1. Because they required no external support circuitry and their six I/O pins were often more than enough for a single application, the PIC12Cxxx controllers were being spread around like mad, replacing special function chips (such as the venerable 555 timer) in designs everywhere.

Recently unveiled is a new family of microcontrollers that provide a glimpse into the future. The PIC18Cxxx family is Microchipýs new foray into the high-end 8-bit market. While not perfect, these chips go a long way towards establishing a viable high-end presence for Microchip.

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