THROUGH THE LOOKING GLASS

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THROUGH THE LOOKING GLASS

Lessons from the Trenches Taking a Look at the PIC18Cxxx Series
by David Brobst

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

PIC18Cxxx CHIPS

The current offering of the PIC18Cxxx architecture is limited to the PIC18Cxx2 family. In keeping with the tradition of vertically scaled subfamilies in controller lines, there are four chips in the PIC18Cxx2 familyıPIC18C452, PIC18C442, PIC18C252, and PIC18C242. The number of I/O lines and amount of program/data memory are the only differentiating features among the four chips. Table 1 details some of the features for this line of controllers. Figure 1 shows a pinout of both the 28- and 40-pin chips.

Feature/device	18C452	18C442	18C252	18C242
Package	40-pin DIP & SOIC 44-pin PLCC 40-pin TQFP	40-pin DIP & SOIC 44-pin PLCC 40-pin TQFP	28-pin DIP & SOIC	28-pin DIP & SOIC
I/Os	34	34	23	23
Program memory	16384 instructions	8192 instructions	16384 instructions	8192 instructions
Data memory	1536 bytes	512 bytes	1536 bytes	512 bytes
Clock speed	40 MHz	40 MHz	40 MHz	40 MHz
A/D (10 bit)	8	8	5	5
Programmable brownout	Yes	Yes	Yes	Yes
Programmable low voltage	Yes	Yes	Yes	Yes
USART	Yes	Yes	Yes	Yes
SPI	Yes	Yes	Yes	Yes
I²C (Master)	Yes	Yes	Yes	Yes
PWM (10 bit)	2	2	2	2
Timers	4	4	4	4
Hardware multiply	8 ı 8 single instruction	8 ı 8 single instruction	8 ı 8 single instruction	8 ı 8 single instruction

Table 1ıHere are the 18Cxx2 controller features. In addition to the standard features, note the large amount of program and data memory.

After looking at Table 1 and Figure 1, a few things are blessedly obvious for anyone familiar with the mid-range family of PIC microcontrollers. First and foremost, the 28- and 40-pin devices in the PIC18Cxx2 family share the exact same pinout as the 28- and 40-pin devices of the entire PIC16Cxxx family of microcontrollers. This means that current designs can potentially migrate to the more powerful chip without a costly hardware revision. At the very least, keeping the same pinout eases the design because all of the I/Os and special function modules are in familiar spots.

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