CMD_CLEAR 
     CMD_FLUSH 
     CMD_READ 
     CMD_RESET 
     CMD_START 
     CMD_STOP 
     CMD_WRITE 
     OpenDevice() 
     PDCMD_QUERY 
     PDCMD_SETPARAMS 

   NAME
	Clear -- clear the parallel port buffer

   FUNCTION
	This command just RTS's (no buffer to clear)

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_CLEAR (05)

   NAME
	Flush -- clear all queued I/O requests for the parallel port

   FUNCTION
	This command purges the read and write request queues for the
	parallel device. The currently active request is not purged.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_FLUSH (08)

   NAME
	Read -- read input from parallel port

   FUNCTION
	This command causes a stream of characters to be read from the
	parallel I/O register. The number of characters is specified in
	io_Length. The EOF and EOL modes are supported, but be warned that
	using these modes can result in a buffer overflow if the proper
	EOL or EOF character is not received in time. These modes should
	be used only when the sender and receiver have been designed to
	cooperate. A safety guard can be implemented to EOF by setting
	io_Length to a maximum allowed value. That cannot be done with EOL
	since the EOL mode is identified by io_Length=-1.

	The parallel.device has no internal buffer; if no read request has
	been made, pending input (i.e. handshake request) is not
	acknowledged.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_READ (02)
	io_Flags        If IOF_QUICK is set, driver will attempt Quick IO
	io_Length       number of characters to receive.
	io_Data         pointer where to put the data.

   RESULTS
	io_Error -- if the Read succeded, then io_Error will be null.
	    If the Read failed, then io_Error will contain an error code.

   SEE ALSO
	parallel.device/PDCMD_SETPARAMS

   NAME
	Reset -- reinitializes the parallel device

   FUNCTION
	This command resets the parallel device to its freshly initialized
	condition. It aborts all I/O requests both queued and current and
	sets the devices's flags and parameters to their boot-up time 
	default values. At boot-up time the PTermArray is random, and it
	will be so also here.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_RESET (01)

   RESULTS
	Error -- if the Reset succeded, then io_Error will be null.
	         if the Reset failed, then the io_Error will be non-zero.

   NAME
	Start -- restart paused I/O over the parallel port

   FUNCTION
	This command restarts the current I/O activity on the parallel
	port by reactivating the handshaking sequence.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_START (07)

   SEE ALSO
	parallel.device/CMD_STOP

   NAME
	Stop -- pause current activity on the parallel device

   FUNCTION
	This command halts the current I/O activity on the parallel
	device by discontinuing the handshaking sequence. The stop and
	start commands may not be nested.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_STOP (06)

   SEE ALSO
	parallel.device/CMD_START

   NAME
	Write -- send output to parallel port

   FUNCTION
	This command causes a stream of characters to be written to the
	parallel output register. The number of characters is specified in
	io_Length, unless -1 is used, in which case output is sent until
	a zero byte occurs in the data. This is independent of, and may be
	used simultaneously with setting the EOFMODE in io_ParFlags and using
	the PTermArray to terminate the read or write.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      CMD_WRITE (03)
	io_Flags        If IOF_QUICK is set, driver will attempt Quick IO
	io_Length       number of characters to transmit, or if set
	                to -1 send until zero byte encountered
	io_Data         pointer to block of data to transmit

   RESULTS
	io_Error -- If the Write succeded, then io_Error will be null.
	     If the Write failed, then io_Error will contain an error code.

   SEE ALSO
	parallel.device/PDCMD_SETPARAMS

   NAME
	Open -- a request to open the parallel port

   SYNOPSIS
	error = OpenDevice("parallel.device", unit, ioExtPar, flags)
	D0                  A0                D0    A1        D1

   FUNCTION
	This function allows the requestor software access to the parallel
	device.  Unless the shared-access bit (bit 5 of io_ParFlags) is
	set, exclusive use is granted and no other access is allowed
	until the owner closes the device.

	A FAST_MODE, can be specified (bit 3 of io_Parflags) to speed up
	transfers to high-speed printers. Rather than waiting for the printer
	to acknowledge a character using the *ACK interrupt, this mode will
	send out data as long as the BUSY signal is low. The printer must be
	able to raise the BUSY signal within 3 micro-seconds on A2630s,
	otherwise data will be lost. Should be used only in an exclusive-
	access Open().

	A SLOWMODE mode can be specified (bit 4 of io_ParFlags) when very
	slow printers are used. If the printer acknowledges data at less
	than 5000 bytes per second, then this mode will actually save CPU
	time, although it consumes much more with high-speed printers.

	The PTermArray of the ioExtPar is initialized only if the EOFMODE
	bit (bit 1 of io_ParFlags) is set. The PTermArray can be further
	modified using the PDCMD_SETPARAMS command.

   INPUTS
	"parallel.device" - a pointer to literal string "parallel.device"
	unit - Must be zero for future compatibility
	ioExtPar - pointer to an IO Request block of structure IOExtPar to
		   be initialized by the Open() function. The io_ParFlags
		   field must be set as desired.
	flags - Must be zero for future compatibility

   RESULTS
	d0 -- same as io_Error
	io_Error -- if the Open succeded, then io_Error will be null.
		    If the Open failed, then io_Error will be non-zero.

   SEE ALSO
	exec/CloseDevice

   NAME
	Query -- query parallel port/line status

   FUNCTION
	This command return the status of the parallel port lines and
	registers. 

   IO REQUEST
	io_Message      must have mn_ReplyPort initialized
	io_Device       set by OpenDevice
	io_Unit         set by OpenDevice
	io_Command      PDCMD_QUERY (09)

   RESULTS
	io_Status        BIT  ACTIVE  FUNCTION

	                 0     high   printer busy toggle (offline)
	                 1     high   paper out
	                 2     high   printer selected on the A1000
	                              printer selected & serial "Ring
	                              Indicator" on the A500/A2000
	                              Use care when making cables.
	                 3      -     read=0,write=1
	               4-7            reserved

   BUGS
	In a earlier version of this AutoDoc, BUSY and PSEL were reversed.
	The function has always been correct.

   NAME
	SetParams -- change parameters for the parallel device

   FUNCTION
	This command allows the caller to change the EOFMODE parameter for
	the parallel port device. It will disallow changes if any reads or
	writes are active or queued.  

	The PARB_EOFMODE bit of io_ParFlags controlls whether the
	io_PTermArray is to be used as an additional termination criteria
	for reads and writes.  It may be set directly without a call to
	SetParams, setting it here performs the additional service of
	copying the PTermArray into the device default array which is used
	as the initial array for subsequent device opens. The Shared bit
	can be changed here, and overrides the current device access mode
	set at OpenDevice time.

   IO REQUEST
	io_Message      mn_ReplyPort initialized
	io_Device       preset by OpenDevice
	io_Unit         preset by OpenDevice
	io_Command      PDCMD_SETPARAMS (0A)
  			NOTE that the following fields of your IORequest
	                are filled by Open to reflect the parallel device's
	                current configuration.
	io_PExtFlags    must be set to zero, unless used
	io_ParFlags     see definition in parallel.i or parallel.h
	                NOTE that x00 yields exclusive access, PTermArray
	                inactive.
	io_PTermArray   ASCII descending-ordered 8-byte array of
	                termination characters. If less than 8 chars
	                used, fill out array w/lowest valid value.
	                Terminators are used only if EOFMODE bit of
	                io_Parflags is set. (e.g. x512F040303030303 )
	                This field is filled on OpenDevice only if the
	                EOFMODE bit is set.

   RESULTS
	io_Error -- if the SetParams succeded, then io_Error will be null.
	            if the SetParams failed, then io_Error will be non-zero.