Mode--Block Output or Concurrent I/O

There are two different modes of using the a port, called BLOCK OUTPUT and CONCURRENT I/0.

Block Output:

Block output is used only for output from the computer to the ATARI 850 Interface Module. A block output is effected by the BASIC commands PRINT and PUT to a properly OPENed port.

The contents of the Buffer can be sent at any time (before it fills) by the Command FORCE SHORT BLOCK, described in the section called Forcing Early Transmission of Output Blocks.

Concurrent I/O Mode:

To receive information from the ATARI 850 Interface Module you must use this mode It supports Full duplex communication with the Interface Module To use this mode~ first OPEN a File for I/O then give the START CONCURRENT I/O MODE command (XIO 40). then use the BASIC commands INPUT. GET, PRINT or PUT in this made, BASIC is executing other instructions while I/O is proceeding. Incoming characters From a port are stored in a buffer. You may get the contents of the buffer at any time by INPUTing from that port.

Warnings and Restrictions

You must observe certain precautions when you use Concurrent Mode I/O the only I/O operations that are permitted with this mode are GET, INPUT, PUT, PRINT, STATUS and CLOSE to the OPENed port, and I/O to the Keyboard and Screen (which do not involve any peripheral device).

Using one Port for concurrent I/O prevents the use of any other port of the Interface Module, including the Printer Port. The other ports remain inaccessible until you terminate the concurrent I/O mode. You terminate concurrent I/O by CLOSEing the port.

During Concurrent I/O, incoming data may overflow the computer's buffer. In that case, data is lost. Methods for avoiding loss of data in this way are described in APPENDIX 8.

After you have started Concurrent Mode I/O, you can not configure a port. Therefore, all configuration commands (XIO 34, XIO 36 and XIO 38) must be executed before a START CONCURRENT MODE I/O command.

Once set, configured parameters will not change until you change them with an appropriate command. Pressing SYSTEM RESET on the computer console will NOT reset any parameter to its default value. Turning off the power on the Interface Module may reset some parameters but not others and may result in peculiar operation as information about some of these parameters is saved both in the computer and in the Interface Module. Turning off the power to the Interface module during a session with the computer is not recommended. Turning off the power to the computer also resets the Interface Module. When you turn the computer back on, and the Interface module auto-boots (see the section on automatic bootstrapping in APPENDIX 11), all of the above parameters will have reverted to their pre-set default values.

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