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Intel 8080 Assembler

The following text is an exert from the Assembly language article.

In computer programming, assembly language (or assembler language), sometimes abbreviated asm, is any low-level programming language in which there is a very strong correspondence between the instructions in the language and the architecture's machine code instructions. Assembly language usually has one statement per machine instruction (1:1), but constants, comments, assembler directives, and symbolic labels of, e.g., memory locations, registers, and macros are generally also supported.

Intel 8080 Assembly Language Programming Manual​

For more information, refer to:

Assemble assembly applications​

The CP/M disk image includes two demo assembly applications, DEMO.ASM and SLEEP.ASM. Follow these steps to edit, assemble, and load the demo file:

The DEMO.ASM example​

  1. List the DEMO.ASM file

    type sleep.asm
            ORG     0100H           ; CP/M base of TPA (transient program area)
            OUT     30
            MVI     C,09H           ; Print string function
            LXI     D,MESSAGE       ; Point
            CALL    0005H           ; Call bdos
            RET                     ; To cp/m
    MESSAGE:DB      0DH,0AH,'Hello, World!',0DH,0AH,'$'
            END

  2. Assemble the DEMO.ASM file:

    asm demo

  3. Load and link the assembled code:

    load demo

  4. Run the demo application:

    demo

Edit a file with Word-Master​

in the following steps use the Word-Master text editor to edit a file. It's highly recommended to edit files with Visual Studio Code and then copy the file to the Altair filesystem using the CP/M gf command.

  1. Edit the DEMO.ASM file with Word-Master:

    wm demo.asm

  2. Switch the web terminal to character input mode by selecting Ctrl+L.

  3. Edit the demo.asm file. For example, change Hello, World! text to your name.

  4. Save your updates to the demo.asm file:

    1. Select the Esc key.
    2. Select E to exit. Your file changes are saved to disk.

  5. Switch the web terminal to line input mode by selecting Ctrl+L.

  6. Then assemble, load, and run the updated demo.asm application.

Sleep assembly example​

The SLEEP.ASM example uses Intel 8080 input and output port instructions. The SLEEP.ASM application sets a sleep period of 2 seconds using output port 30, waits on input port 30 for the delay period to expire, and then publishes weather data to Azure IoT Central. For more information about Intel 8080 IO port mappings, refer to Intel 8080 input and output ports.

  1. List the SLEEP.ASM file

    type sleep.asm
          ORG 0100H   ;CP/M base of TPA (transient program area)
          MVI C,09H   ;Print string function
          LXI D,MSG   ;Point to waiting message
          CALL 0005H  ;Call bdos
          MVI A,2     ;Move 2 to the accumulator to set a 2 second delay
          OUT 30      ;Start timer
    LOOP: IN 30       ;Get delay timer state into the accumulator
          CPI 00H     ;If accumulator equal to 0 then timer has expired
          JZ BACK     ;Jump on zero
          JMP LOOP
    BACK: MVI C,09H   ;Print string function
          LXI D,PUB   ;Point to publish message
          CALL 0005H  ;Call bdos
          MVI A,0H    ;Move zero to the accumulator
          OUT 32      ;Publish to Azure IoT Central
          MVI C,09H   ;Print string function
          LXI D,FINI  ;Point to Finished message
          CALL 0005H  ;Call Bdos
          RET
    MSG:  DB 'Sleeping 2 seconds$'
    FINI: DB 0DH,0AH,'Finished$'
    PUB:  DB 0DH,0AH,'Publishing to Azure IoT Central$' 
          END

  2. Assemble the SLEEP.ASM file:

    asm sleep

  3. Load and link the assembled code:

    load sleep

  4. Run the demo application:

    sleep