Introduction

Some of the devices currently in the 3DO system include:

Timer device
File device
SPORT device
CD-ROM device (not documented here)
RAM device (not documented here)
xbus device (not documented here)

All devices use I/O request items for communicating information between tasks and the device. Refer to The Portfolio I/O Model, for more information on devices and I/O requests.

The first step in the I/O process is for the task to open the device with the OpenNamedDevice() call.

A task must also get its own IOReq and IOInfo data structures to pass information to and from the device. The IOReq data structure is created using the call CreateIOReq(). The IOInfo data structure is allocated by the task either via a memory allocation call or on the stack.

Note: The IOInfo structure must be cleared of all unused bits before it is used.

After setting the IOInfo fields, a task uses the SendIO() or DoIO() functions to pass the item number of the I/O request structure and a pointer to the IOInfo structure to the device. The I/O request is passed to the device, and the appropriate action is taken by the device as specified by the IOInfo structure fields.