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11.COSMAC VIP Operation

COSMAC VIP is operated with the RUN switch and hex keyboard. The PWR light shows that power is on. The Q light is activated by various programs. A tone is sounded whenever the Q light is on. The TAPE light glows when cassette input data is present. When using COSMAC VIP, always start with the RUN switch in the down (or reset) position. Flipping the RUN switch up initiates execution of machine language programs beginning at memory location 0000. If you have previously stored the CHIP-8 Ian_ guage interpreter program at locations 0000-01FF, execution of a program written in this language will begin at 0200. To manually terminate execution of any program, flip RUN down.

Using the Operating System

With COSMAC VIP you can load programs into memory from the hex keyboard or cassette recorder, record the contents of memory on cassettes, show the contents of memory bytes in hex form on the display, and examine the contents of CDP1802 microprocessor registers. These functions are performed with the aid of a special program called an operating system. This operating system is contained in a ROM so that it's ready to use as soon as power is turned on. It is located at memory locations 8000-81FF. A machine code listing and summary of this operating system is provided in Appendix B.

To use the operating system hold key C down on the hex keyboard when you flip RUN up. You will hear a tone. Release key C and you're ready to use the operating system.

After selecting the operating system you can do four different operations as shown in the following table:

KEY

OPERATION

0

MW (Memory Write)

A

MR (Memory Read)

F

TW (Tape Write) TR

B

(Tape Read)

For any of these operations you must first enter a memory address. Enter the 4 hex digits of any memory address using the hex keyboard (most significant digit first). You will see the address at the lower left of the screen and the byte contained in that address at the lower right. Remember that addresses and bytes are always entered and shown in hex form. Suppose you entered 0200. You will see 0200 at the bottom left of the screen and the byte stored at 0200 at the lower right.

Memory Write

If you want to change this byte, press the 0 key. Now press two digits of the new byte (most significant digit first) and it will be stored at 0200 replacing the original byte. You will see this change on the screen. If you enter another byte it will be shown and stored at the next higher address in sequence (0201 in this example). You can load any, sequence of bytes directly from the hex keyboard in this manner. If you make a mistake, flip RUN down. With key C pressed, flip RUN back up. Enter the address at which you made the error. Press key 0 and resume entering your program.

Note the random bit pattern on the screen above the hex display. This pattern is the binary data

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RCA CDP18S711 manual COSMAC VIP Operation, Using the Operating System, Memory Write