ICD Multi I/O Board Manual (Rev 5/20/1987) Introduction to the MIO

Chapter 1 Introduction to the MIO Index

General Functions

The ICD Multi I/O board (MIO) is a complex peripheral device which adds exceptional power to the Atari 800XL or 130XE computer. The MIO gives the user five additional hardware functions not available with a stock 8-bit Atari computer. These are: a parallel printer interface, a serial interface for printer or MODEM, a printer buffer, a bootable RAMDISK, and an SCSI/SASI interface for hard disk drives. An optional sixth function (80 column board) may be added at a later date.

Parallel Port

This is a "centronics" type parallel port for connection to printers. The hardware connection uses a 15 pin sub D connector like the P:R: Connection or Atari 850 interface. All the pin connections are the same so the inexpensive P:R: Connection/850 cables will work to connect to your printer. See Chapter 2 and Appendix B for the complete pinout and connection diagram.

Serial Port

The serial port is an RS-232 type port for connection to serial printers, MODEMs or other computers. It uses a 9 pin sub D connector with the same pinouts as port 1 of the P:R: Connection or Atari 850 interface. See Chapter 2 and Appendix B for the complete pinout and connection diagram. The "R:" handler (in ROM) is equivalent to the P:R: Connection in compatibility, however, no memory inside your computer is used for the handler (since the "R:" handler is built into the ROM on the MIO). See Appendix C for complete compatibility information. You may also use the serial port to control a serial printer. Full XON/XOFF software handshake protocol and READY/BUSY hardware handshake protocol is supported through the "P:" handler on this port.


The RAM is available for use as RAMDISKs and/or a printer spooler (commonly called a printer buffer). Since the MIO has its own power supply and refresh oscillator, memory is retained even after powering down the computer. This unique feature along with drive swapping allows rebooting the computer directly from RAMDISK!

The MIO is available in 256K or 1 Meg versions. The RAM chips are not socketed and are a very special variety. The 256K versions are not user upgradeable! They may be upgraded by sending the MIO along with the correct upgrade fee to ICD's service department. (Call for current prices.) Any user modification attempts will void all warranties and result in additional service fees.

SCSI/SASI Interface

The SCSI/SASI interface allows the use of standard SCSI and SASI devices. These include hard disk drives, tape backup units, and whatever else is available with these protocols. Chapter 2 lists many of the current devices supported by this interface and the current software.


The ROM (16K bytes) in the MIO contains all the control software for the various features of the MIO. The built in MENU program is accessed by holding down the SELECT key while booting or by holding down SELECT and pressing RESET. Since the MENU loads into the computer's main memory (RAM), this action destroys the previous contents of program memory (computer RAM not the MIO RAM). To return to DOS (or cartridge) press RESET or '0'.

The MENU allows setting the configuration for your particular application and saving new default parameters to hard drive #0,0. This includes: assigning drives, partitioning them, setting the printer buffer, assigning ports, and selecting the R: handler if desired. One of the benefits of the MIO and the parallel bus is that the various handlers are MIO resident and do not need to load into machine memory as required by serial bus devices. This saves valuable memory since MEMLO remains unchanged.

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