The PIC16F627A/628A/648A is 18-pin Flash-based member of the versatile PIC16F627A/628A/648A family of low-cost, high-performance, CMOS, fully static, 8-bit microcontrollers. All PIC® microcontrollers employ an advanced RISC architecture. The PIC16F627A/628A/648A has enhanced core features, an eight-level deep stack, and multiple internal and external interrupt sources. The separate instruction and data buses of the Harvard architecture allow a 14-bit wide instruction word with the separate 8-bit wide data. The two-stage instruction pipeline allows all instructions to execute in a single cycle, except for program branches (which require two cycles). A total of 35 instructions (reduced instruction set) are available, complemented by a large register set.PIC16F627A/628A/648A microcontrollers typically achieve a 2:1 code compression and a 4:1 speed improvement over other 8-bit microcontrollers in their class. PIC16F627A/628A/648A devices have integrated features to reduce external components, thus reducing system cost, enhancing system reliability, and reducing power consumption. The PIC16F627A/628A/648A has 8 oscillator configurations. The single-pin RC oscillator provides a low-cost solution. The LP oscillator minimizes power consumption, XT is a standard crystal, and INTOSC is a self-contained precision two-speed internal oscillator. The HS mode is for High-Speed crystals. The EC mode is for an external clock source. The Sleep (Power-down) mode offers power savings. Users can wake-up the chip from Sleep through several external interrupts, internal interrupts and Resets. A highly reliable Watchdog Timer with its own on-chip RC oscillator provides protection against software lockup. Table 1-1 shows the features of the PIC16F627A/628A/648A mid-range microcontroller family. A simplified block diagram of the PIC16F627A/628A/648A is shown in Figure 3-1. The PIC16F627A/628A/648A series fits in applications ranging from battery chargers to low power remote sensors. The Flash technology makes customizing application programs (detection levels, pulse generation, timers, etc.) extremely fast and convenient. The small footprint packages makes this microcontroller series ideal for all applications with space limitations. Low cost, low power, high performance, ease of use and I/O flexibility make the PIC16F627A/628A/648A very versatile. This product is known as PIC16F628A-I/P, PIC16F628A-I/ML, PIC16F628A-E/P, PIC16F628A-I/SS, PIC16F628A-E/SS, PIC16F628AT-I/SS, PIC16F628A-I/SO, PIC16F628-04/SS.