DIO__GetDeviceUnits (ul_pbar_dio)

 *  Synopsis:
 *    #include <ul_pbar_dio:dio.h>
 *
 *    char *DIO__GetDeviceUnits( const CDIOptr devicePtr, char *deviceUnits )
 *
 *  Function intent:
 *    DIO__GetDeviceUnits() returns a pointer to a string containing the DIO
 *    device units text for the device pointed to by devicePtr.  If
 *    parameter deviceUnits is not NULL the routine places the string in
 *    memory pointed to by deviceUnits and returns deviceUnits.  If parameter
 *    deviceUnits is NULL the routine returns a pointer to the DIO__ system's
 *    copy of the string.
 *  Function parameters:
 *    CDIOptr	devicePtr	The unique DIO device I/O control pointer
 *                              returned by DIO__InitializeModule().
 *    char	*deviceUnits	destination array of LEN_DEV_UNITS + 1 bytes
 *  Function return value:
 *    none