viMapAddress/viMapAddressEx

NI-VISA 15.0 Help

Edition Date: June 2015

Part Number: 370131S-01

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Purpose

Maps the specified memory space into the process's address space.

C Syntax

ViStatus viMapAddress(ViSession vi, ViUInt16 mapSpace, ViBusAddress mapBase, ViBusSize mapSize, ViBoolean access, ViAddr suggested, ViPAddr address)

ViStatus viMapAddressEx(ViSession vi, ViUInt16 mapSpace, ViBusAddress64 mapBase, ViBusSize mapSize, ViBoolean access, ViAddr suggested, ViPAddr address)

Visual Basic Syntax

viMapAddress&(ByVal vi&, ByVal mapSpace%, ByVal mapBase&, ByVal mapSize&, ByVal access%, ByVal suggested&, address&)

Resource Classes

PXI INSTR, PXI MEMACC, VXI INSTR, VXI MEMACC

Parameters

Name Direction Description

vi

IN

Unique logical identifier to a session.

mapSpace

IN

Specifies the address space to map. Refer to the Description section for more information.

mapBase

IN

Offset (in bytes) of the memory to be mapped. Refer to the Description section for more information. For viMapAddress(), this is a 32-bit value for 32-bit applications and a 64-bit value for 64-bit applications. For viMapAddressEx(), this is always a 64-bit value.

mapSize

IN

Amount of memory to map (in bytes).

access

IN

VI_FALSE (0).

suggested

IN

If suggested parameter is not VI_NULL (0), the operating system attempts to map the memory to the address specified in suggested. There is no guarantee, however, that the memory will be mapped to that address. This operation may map the memory into an address region different from suggested.

address

OUT

Address in your process space where the memory was mapped.

Return Values

Completion Codes Description

VI_SUCCESS

Mapping successful.

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_INV_SPACE

Invalid address space specified.

VI_ERROR_INV_OFFSET

Invalid offset specified.

VI_ERROR_NSUP_OFFSET

Specified region is not accessible from this hardware.

VI_ERROR_TMO

viMapAddress() could not acquire resource or perform mapping before the timer expired.

VI_ERROR_INV_SIZE

Invalid size of window specified.

VI_ERROR_ALLOC

Unable to allocate window of at least the requested size.

VI_ERROR_INV_ACC_MODE

Invalid access mode.

VI_ERROR_WINDOW_MAPPED

The specified session already contains a mapped window.

VI_ERROR_INV_SETUP

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

Description

The viMapAddress() operation maps in a specified memory space. The memory space that is mapped is dependent on the type of interface specified by the vi parameter and the mapSpace parameter. The address parameter returns the address in your process space where memory is mapped. The following table lists the valid entries for the mapSpace parameter.

Value Description

VXI and VME

VI_A16_SPACE (1)
VI_A24_SPACE (2)
VI_A32_SPACE (3)
VI_A64_SPACE (4)

PXI INSTR

VI_PXI_CFG_SPACE (10)
VI_PXI_BAR0_SPACE (11) to VI_PXI_BAR5_SPACE (16)

PXI MEMACC

VI_PXI_ALLOC_SPACE (9)

Note  On some hardware platforms, the low-level driver may have limitations on the parameters to this function. For example, on VXI resources mapBase should be a multiple of mapSize for best results. If these limitations prevent NI-VISA from mapping the full region you request (mapSize bytes starting at mapBase), the function will return an error such as VI_ERROR_NSUP_OFFSET or VI_ERROR_ALLOC.

INSTR Specific

Notice that mapBase specified in the viMapAddress() operation for an INSTR Resource is the offset address relative to the device's allocated address base for the corresponding address space that was specified. For example, if mapSpace specifies VI_A16_SPACE, then mapBase specifies the offset from the logical address base address of the specified VXI device. If mapSpace specifies VI_A24_SPACE or VI_A32_SPACE, then mapBase specifies the offset from the base address of the VXI device's memory space allocated by the VXI Resource Manager within VXI A24 or A32 space.

MEMACC Specific

For a MEMACC Resource, the mapBase parameter specifies an absolute address.

Note  The output address is not necessarily always a pointer. It may be possible for viMapAddress to succeed and output a token address value of 0. This is not the same as a NULL pointer, even though the value of NULL is 0. Obviously, this situation cannot happen if the address is a pointer that the user can dereference. Regardless, you should determine whether viMapAddress succeeded or failed by checking the returned status, not the output value of the address.


Related Topics

INSTR Resource

MEMACC Resource

viUnmapAddress

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