Command Operation ------- --------- CMD_FLUSH Purge all queued requests for the parallel device. Does not affect active requests. CMD_READ Read a stream of characters from the parallel port. The number of characters can be specified or a termination character(s) can be used. CMD_RESET Reset the parallel port to its initialized state. All active and queued I/O requests will be aborted. CMD_START Restart all paused I/O over the parallel port. Reactivates the handshaking sequence. CMD_STOP Pause all active I/O over the parallel port. Deactivates the handshaking sequence. CMD_WRITE Write out a stream of characters to the parallel port. The number of characters can be specified or a NULL-terminated string can be sent. PDCMD_QUERY Return the status of the parallel port lines and registers. PDCMD_SETPARAMS Set the parameters of the parallel port. Exec Functions as Used in This Chapter -------------------------------------- AbortIO() Abort a command to the parallel device. If the command is in progress, it is stopped immediately. If it is queued, it is removed from the queue. BeginIO() Initiate a command and return immediately (asynchronous request). This is used to minimize the amount of system overhead. CheckIO() Determine the current state of an I/O request. CloseDevice() Relinquish use of the parallel device. All requests must be complete. DoIO() Initiate a command and wait for completion (synchronous request). OpenDevice() Obtain use of the parallel device. SendIO() Initiate a command and return immediately (asynchronous request). WaitIO() Wait for the completion of an asynchronous request. When the request is complete the message will be removed from your reply port. Exec Support Functions as Used in This Chapter ---------------------------------------------- CreateExtIO() Create an extended I/O request structure of type IOExtPar. This structure will be used to communicate commands to the parallel device. CreatePort() Create a signal message port for reply messages from the parallel device. Exec will signal a task when a message arrives at the port. DeleteExtIO() Delete an extended I/O request structure created by CreateExtIO(). DeletePort() Delete the message port created by CreatePort().
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