M6800 Assembly Language Programming - PUCRS

1 M6800 Assembly Language Programming 2 3. MC6802 MICROPROCESSOR MC6802 microprocessor runs in 1 MHz clock cycle. It has 64 Kbyte memory address capacity using 16-bit addressing path (A0-A15). The 8-bit data path (D0-D7) is bidirectional and has three states. It has 72 instructions which are 1, 2 or 3 byte instructions. MC6802 microprocessor has 3 interrupt inputs. One of them is maskable (IRQ), the other one is unmaskable (NMI) and the last one is the reset (RESET). It also has 2 special instructions: SWI (software interrupt) and WAI (wait for interrupt). MC6802 s pin numbers and their connections are shown in Figure Figure - MC6082 Microprocessor REGISTERS MC6802 Microprocessor has three 16-bit registers and three 8-bit registers available for use by the programmer (Figure ).

6 All branch operations use relative addressing mode. Branches can be forward or backward. The program in Figure 3.5 is an example for the use of branch instructions. In the first branch instruction (BRA NEXT), the address to be branched is 109 H. As relative addressing is used, the offset is calculated as 109 H - 105 H = 04 H where 105 H

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