viClear

NI-VISA 15.0 Help

Edition Date: June 2015

Part Number: 370131S-01

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Purpose

Clears a device.

C Syntax

ViStatus viClear(ViSession vi)

Visual Basic Syntax

viClear&(ByVal vi&)

Resource Classes

GPIB INSTR, Serial INSTR, TCPIP INSTR, TCPIP SOCKET, USB INSTR, USB RAW, VXI INSTR

Parameters

Name Direction Description

vi

IN

Unique logical identifier to a session.

Return Values

Completion Codes Description

VI_SUCCESS

Operation completed successfully.

Error Codes Description

VI_ERROR_INV_OBJECT

The given session reference is invalid.

VI_ERROR_NSUP_OPER

The given vi does not support this operation.

VI_ERROR_RSRC_LOCKED

Specified operation could not be performed because the resource identified by vi has been locked for this kind of access.

VI_ERROR_TMO

Timeout expired before operation completed.

VI_ERROR_RAW_WR_PROT_VIOL

Violation of raw write protocol occurred during transfer.

VI_ERROR_RAW_RD_PROT_VIOL

Violation of raw read protocol occurred during transfer.

VI_ERROR_BERR

Bus error occurred during transfer.

VI_ERROR_NCIC

The interface associated with the given vi is not currently the controller in charge.

VI_ERROR_NLISTENERS

No-listeners condition is detected (both NRFD and NDAC are unasserted).

VI_ERROR_INV_SETUP

Unable to start operation because setup is invalid (due to attributes being set to an inconsistent state).

VI_ERROR_CONN_LOST

The I/O connection for the given session has been lost.

Description

The viClear() operation clears the device input and output buffers. The bus-specific details are:

Clear for 488.2 Instruments (GPIB, VXI, TCPIP, and USB)

  • For a GPIB device, VISA sends the Selected Device Clear command.
  • For a VXI device, VISA sends the Word Serial Clear command.
  • For a USB device, VISA sends the INITIATE_CLEAR and CHECK_CLEAR_STATUS commands on the control pipe.

Clear for Non-488.2 Instruments (Serial INSTR, TCPIP SOCKET, and USB RAW)

  • For Serial INSTR sessions, VISA flushes (discards) the I/O output buffer, sends a break, and then flushes (discards) the I/O input buffer.
  • For TCPIP SOCKET sessions, VISA flushes (discards) the I/O buffers.
  • For USB RAW sessions, VISA resets the endpoints referred to by the attributes VI_ATTR_USB_BULK_IN_PIPE and VI_ATTR_USB_BULK_OUT_PIPE.

Invoking viClear() also discards the read and write buffers used by the formatted I/O services for that session.


Related Topics

INSTR Resource

SOCKET Resource

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