Designing Embedded Hardware, 2nd Edition

A Bigger PIC

In this section, we'll look at the PIC16C73 processor. For a mid-range PIC, the design is not dissimilar to the simpler PIC we've already seen. The only real difference is that the processor has more pins, more I/O, and more functionality. Designing for PIC17 and PIC18 processors is not dissimilar to creating machines based on the PIC16 family. What you learn here is applicable to many other PICs.

The schematic for this processor is shown in Figure 14-5. This processor has 4K words of program memory, 192 bytes of RAM, and a variety of I/O subsystems, such as three timer modules, SPI, I₂C, a UART, five channels of analog input, and up to 22 digital I/O pins.

Figure 14-5. PIC16C73 processor and support components

This processor has one power pin (VDD) and two ground pins (VSS). As always, power is decoupled to ground with a small capacitor (C3). The only other requirements are some form of clock generation—in this case provided by a crystal, X1--and two decoupling capacitors, C1 and C2. The clock could just as easily have been provided using an RC circuit, as we saw with the 12C508 PIC. The reset input, , is tied directly to the power supply, such that it is permanently inactive. In this case, we are relying on the processor's internal power-on reset circuitry and don't ...