Gilderflukeco old MACs 8 bit Digital Audio System Manual do Utilizador descarregar pdf (Página 60)

- Serial Port Commands -

The MACs digital audio system can be controlled by simple switch closures to start and stop playback

or looping, mute the audio, and perform a variety of functions. In addition to this method of controlling

the Repeater cards, you can talk to any or all of the cards at one time through a serial data line from

your computer, terminal, or control system.

All commands sent to the MACs digital audio system through its serial interface take the following

format. All characters are sent in ASCII. All numeric values are sent in HEXadecimal (HEX for short), and

consist of one or more ASCII characters (0-9, A through F). The case (as in upper and lower) of all input is

important. A lower case 'a' signifies a command, while an 'A' is a numeric value. If the digital audio

system receives another command while it is waiting for additional input needed to complete the

previous command, it will abandon the previous command and start working on the new one.

In the following documentation any input you will send to the audio system is shown in o u t l i n e. The

response to a command is shown in

italics

If the digital audio system is in a mode where you expect to receive some response from it (generally

in one of the echo modes), you must wait to receive all of the characters you are expecting before

sending the system a new command. The reason for this is that you are actually talking to up to 256

microprocessors at a time, and if you issue a command which gives a response from one card, and

then a command which gives a response from a second card before the first has finished, then the two

may try to output data at the same time. This won't cause any damage, but may result in garbled data

at the receiver.

It is also possible to overload the digital audio system with too many commands through the serial

port. You don't want to take too much time away from the Digital Audio Repeater to serve the serial port.

To communicate with the digital audio system through the serial port, you can use just about any

computer or terminal which has a serial port on it. Some newer computer designs, like the Apple

Macintosh, come with serial ports which are directly compatible with the RS-422 / RS-485 signal levels

the digital audio system wants to see. These signal levels are close enough to be used with the RS-232

signal levels found on most older computers (like most IBM compatibles) with only a simple adapter

cable, so long as the wire isn't too long and there arenÕt too many Repeaters attached to the same

serial line. To gain the full advantage of the RS-422 / RS-485 signal levels you will need to use a signal

level adapter.

If you are using a computer as a terminal you will need to run a modem or terminal emulation

program. These will send everything you type on the keyboard out the serial port on your computer while

printing on the screen anything which comes in from the audio system through the serial port. A modem

program will usually have the advantage over a terminal emulation program in that it will allow you to

save data to your computer's disk drives and then send it back to the audio system at a later date. The

digital audio system uses no screen control codes or ESCape sequences, so it should work on any

machine with a 80 column by 24 line display. Machines with other display formats will work, but may not

look so neat on the screen.

When configuring your modem program, you should set it for 9600 baud, 8 data bits, one stop bit,

and no parity. Higher or lower baud rates can be used if you configure the Digital Audio RepeatersÕ serial

port to run at a different speed. You should set your program not to insert an extra LineFeed (LF)

character after each Carriage Return (CR) it receives. If you are going to be downloading configuration

strings to the system (command ÔsÕ), you will also need to tell the modem program to put a slight delay

between each character sent in order to not over run the Digital Audio RepeatersÕ incoming data buffer.

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