Command        Operation
-------        ---------
TR_ADDREQUEST  Request that the timer device wait a specified period of
               time before replying to the request.

TR_GETSYSTIME  Get system time and place in a timeval structure.

TR_SETSYSTIME  Set the system time from the value in a  timeval structure.


Device Functions
----------------
AddTime()      Add one  timeval structure to another.  The result is placed
               in the first timeval structure.

CmpTime()      Compare one  timeval structure to another.  The result is
               returned as a longword.

GetSysTime()   Get system time and place in a  timeval structure.

ReadEClock()   Read the current 64 bit value of the E-Clock into an
               EClockVal structure.  The count rate of the E-Clock is also
               returned. (V36)

SubTime()      Subtract one timerequest structure from another. The result
               is placed in the first timerequest structure.


Exec Functions as Used in This Chapter
--------------------------------------
AbortIO()      Abort a command to the timer device.

CheckIO()      Return the status of an I/O request.

CloseDevice()  Relinquish use of the timer device. All requests must be
               complete before closing.

DoIO()         Initiate a command and wait for completion (synchronous
               request).

OpenDevice()   Obtain use of the timer device.  The timer device may be
               opened multiple times.

SendIO()       Initiate a command and return immediately (asynchronous
               request).


Exec Support Functions as Used in This Chapter
----------------------------------------------
CreateExtIO()  Create an extended I/O request structure of type
               timerequest.  This structure will be used to communicate
               commands to the timer device.

CreatePort()   Create a signal message port for reply messages from the
               timer device.  Exec will signal a task when a message
               arrives at the reply port.

DeleteExtIO()  Delete the timerequest extended I/O request structure
               created by CreateExtIO().

DeletePort()   Delete the message port created by CreatePort().