Measurement Computing GPIB-488.2 - Manual (Page 4)

1-2 Introduction 978492 GPIB 488.2 Porting Guide
Major Conceptual Differences between IOtech and MCC Routines
Handle-Based vs. Address-Based
Many of the IOtech API calls are handle-based. All devices, when opened successfully via
IOtech API command, are assigned a handle which subsequent calls to the device made
reference to. With the IOtech API it was also possible to assign a name to the device. The
device name could be used to open or close a configured device at a later time; the device name
could also be used to make a duplicate copy (or clone) of a configured device. This functionality
does not exist within the MCC API. The reason lies in the fact that MCC API calls are device
address based.
Single vs. Multiple Devices
In general, IOtech API calls tend to deal with an individual device, whereas many MCC API
calls can deal with multiple devices via an address array. The ‘Minor Modification’ section of
this document provides detailed information regarding this difference.
Error Status Returns
IOtech API calls automatically return an error status. MCC API calls do not. With MCC’s
488.2 GPIB system, it is the responsibility of the programmer to evaluate the error status register,
after a function call is made, and then take the appropriate action to address any error.
Sample
code, for error status checking, is included in the GPIB 488 Projects folder on our web-site,
under Code Examples.
Digital Control
Another difference between IOtech and MCC API pertains to digital control. A user-accessible
digital port exists on the IOtech Personal 488 GPIB card. Because there is no similar MCC 488
board, none of the digital IOtech API commands have an associated MCC command.
Command Terminations
IOtech API includes functionality that deals specifically with send and receive command
termination. The MCC API includes no such send/receive termination commands; however, for
many of the MCC function calls, termination can be set as a parameter.