CHAPTER 2 CENTRAL PROCESSING UNIT 2. CENTRAL PROCESSING UNIT The computer uses 65C02, an enhanced version of its predecessor 6502, as its central processing unit. In the "LASER 128", 1 MHz version is used. In the "LASER 128 EX", 4 MHz version is used. It has the following advantages compared with the NMOS 6502: • Uses CMOS (Complementary Metal Oxide Semiconductor) technology to reduce power consumption and increase noise immunity. • Completely static operation, no lower- limit on CPU clock frequency (can be d.c). • Enhanced instruction set with new instructions and addressing modes. The 65C02 is a 8-bit microprocessor having 16 address lines to access a 64 K-byte address space.
It has one 16-bit program counter, one 8-bit stack pointer, three 8-bit general purpose registers and one 8-bit processor status register. Figure 2-1 shows the programming model. 2-1