Memory Access (MEMACC) Resource

This topic describes the Memory Access (MEMACC) Resource that is provided to encapsulate the address space of a memory-mapped bus, such as the VXIbus.

This section contains information specific to the Windows product.

MEMACC Resource Overview

The Memory Access (MEMACC) Resource encapsulates the address space of a memory-mapped bus such as the VXIbus. A VISA Memory Access Resource, like any other resource, starts with the basic operations and attributes of the VISA Resource Template. For example, modifying the state of an attribute is done via the operation viSetAttribute.

Although the MEMACC resource does not have viSetAttribute listed in its operations, it provides the operation because it is defined in the VISA Resource Template. From this basic set, each resource adds its specific operations and attributes that allow it to perform its dedicated task, such as reading a register or writing to a memory location.

The MEMACC Resource lets a controller interact with the interface associated with this resource. It does this by providing the controller with services to access arbitrary registers or memory addresses on memory-mapped buses.

MEMACC Resource Attributes

AP = Access Privileges

Attribute Name	Attribute Value	Access Privilege		Data Type	Range	Default
Generic MEMACC Resource Attributes
VI_ATTR_DMA_ALLOW_EN	0x3FFF001EUL	RW	Local	ViBoolean	VI_TRUE VI_FALSE	N/A
VI_ATTR_INTF_INST_NAME	0xBFFF00E9UL	RO	Global	ViString	N/A	N/A
VI_ATTR_INTF_NUM	0x3FFF0176UL	RO	Global	ViUInt16	0 to FFFFh	0
VI_ATTR_INTF_TYPE	0x3FFF0171UL	RO	Global	ViUInt16	VI_INTF_VXI VI_INTF_GPIB_VXI VI_INTF_PXI	N/A
VI_ATTR_TMO_VALUE	0x3FFF001AUL	RW	Local	ViUInt32	VI_TMO_IMMEDIATE 1 to FFFFFFFEh VI_TMO_INFINITE	2000 msec.
VXI and GPIB-VXI and PXI Specific MEMACC Resource Attributes
VI_ATTR_DEST_INCREMENT	0x3FFF0041UL	RW	Local	ViInt32	0 to 1	1
VI_ATTR_SRC_INCREMENT	0x3FFF0040UL	RW	Local	ViInt32	0 to 1	1
VI_ATTR_WIN_ACCESS	0x3FFF00C3UL	RO	Local	ViUInt16	VI_NMAPPED VI_USE_OPERS VI_DEREF_ADDR	VI_NMAPPED
VI_ATTR_WIN_BASE_ADDR_32	0x3FFF0098UL	RO	Local	ViBusAddress	N/A	N/A
VI_ATTR_WIN_BASE_ADDR_64	0x3FFF009BUL	RO	Local	ViBusAddress64	N/A	N/A
VI_ATTR_WIN_SIZE_32	0x3FFF009AUL	RO	Local	ViBusSize	N/A	N/A
VI_ATTR_WIN_SIZE_64	0x3FFF009CUL	RO	Local	ViBusSize64	N/A	N/A
VXI and GPIB-VXI Specific MEMACC Resource Attributes
VI_ATTR_DEST_ACCESS_PRIV	0x3FFF0039UL	RW	Local	ViUInt16	VI_DATA_NPRIV VI-DATA_PRIV VI_PROG_NPRIV VI_PROG_PRIV VI_BLCK_NPRIV VI_BLCK_PRIV VI_D64_NPRIV VI_D64_PRIV	VI_DATA_PRIV
VI_ATTR_DEST_BYTE_ORDER	0x3FFF003AUL	RW	Local	ViUInt16	VI_BIG_ENDIAN VI_LITTLE_ENDIAN	VI_BIG_ENDIAN
VI_ATTR_SRC_ACCESS_PRIV	0x3FFF003CUL	RW	Local	ViUInt16	VI_DATA_NPRIV VI_DATA_PRIV VI_PROG_NPRIV VI_PROG_PRIV VI_BLCK_NPRIV VI_BLCK_PRIV VI_D64_NPRIV VI_D64_PRIV	VI_DATA_PRIV
VI_ATTR_SRC_BYTE_ORDER	0x3FFF003DUL	RW	Local	ViUInt16	VI_BIG_ENDIAN VI_LITTLE_ENDIAN	VI_BIG_ENDIAN
VI_ATTR_VXI_LA	0x3FFF00D5UL	RO	Global	ViInt16	0 to 255	N/A
VI_ATTR_WIN_ACCESS_PRIV	0x3FFF0045UL	RW*	Local	ViUInt16	VI_DATA_NPRIV VI-DATA_PRIV VI_PROG_NPRIV VI_PROG_PRIV VI_BLCK_NPRIV VI_BLCK_PRIV	VI_DATA_PRIV
VI_ATTR_WIN_BYTE_ORDER	0x3FFF0047UL	RW*	Local	ViUInt16	VI_BIG_ENDIAN VI_LITTLE_ENDIAN	VI_BIG_ENDIAN
* For VISA 2.2, the attributes VI_ATTR_WIN_BYTE_ORDER and VI_ATTR_WIN_ACCESS_PRIV are RW (readable and writable) when the corresponding session is not mapped ( VI_ATTR_WIN_ACCESS = = VI_NMAPPED). When the session is mapped, these attributes are RO (read only).
VI_ATTR_GPIB_SECONDARY_ADDR	0x3FFF0173UL	RO	Global	ViUInt16	0 to 30, VI_NO_SEC_ADDR	N/A
VI_ATTR_GPIB_PRIMARY_ADDR	0x3FFF0172UL	RO	Global	ViUInt16	0 to 30	N/A
VI_ATTR_INTF_PARENT_NUM	0x3FFF0101UL	RO	Global	ViUInt16	0 to FFFFh	N/A

MEMACC Resource Attribute Descriptions

Attribute Name	Description
Generic MEMACC Resource Attributes
VI_ATTR_DMA_ALLOW_EN	This attribute specifies whether I/O accesses should use DMA ( VI_TRUE VI_FALSE). In some implementations, this attribute may have global effects even though it is documented to be a local attribute. Since this affects performance and not functionality, that behavior is acceptable.
VI_ATTR_INTF_INST_NAME	Human-readable text describing the given interface.
VI_ATTR_INTF_NUM	Board number for the given interface.
VI_ATTR_INTF_TYPE	Interface type of the given session.
VI_ATTR_TMO_VALUE	Minimum timeout value to use, in milliseconds. A timeout value of VI_TMO_IMMEDIATE means that operations should never wait for the device to respond. A timeout value of VI_TMO_INFINITE disables the timeout mechanism.
VXI and GPIB-VXI and PXI Specific MEMACC Resource Attributes
VI_ATTR_DEST_INCREMENT	This is used in the viMoveOutXX operation to specify how much the destination offset is to be incremented after every transfer. The default value of this attribute is 1 (that is, the destination address will be incremented by 1 after each transfer), and the viMoveOutXX operation moves into consecutive elements. If this attribute is set to 0, the viMoveOutXX operation will always write to the same element, essentially treating the destination as a FIFO register.
VI_ATTR_SRC_INCREMENT	This is used in the viMoveInXX operation to specify how much the source offset is to be incremented after every transfer. The default value of this attribute is 1 (that is, the source address will be incremented by 1 after each transfer), and the viMoveInXX operation moves from consecutive elements. If this attribute is set to 0, the viMoveInXX operation will always read from the same element, essentially treating the source as a FIFO register.
VI_ATTR_WIN_ACCESS	Modes in which the current window may be accessed: not currently mapped, through operations viPeekXX and viPokeXX only, or through operations and/or by directly dereferencing the address parameter as a pointer.
VI_ATTR_WIN_BASE_ADDR_32 VI_ATTR_WIN_BASE_ADDR_64	Base address of the interface bus to which this window is mapped.
VI_ATTR_WIN_SIZE_32 VI_ATTR_WIN_SIZE_64	Size of the region mapped to this window.
VXI and GPIB-VXI Specific MEMACC Resource Attributes
VI_ATTR_DEST_ACCESS_PRIV	This attribute specifies the address modifier to be used in high-level access operations, such as viOutXX and viMoveOutXX, when writing to the destination.
VI_ATTR_DEST_BYTE_ORDER	This attribute specifies the byte order to be used in high-level access operations, such as viOutXX and viMoveOutXX, when writing to the destination.
VI_ATTR_SRC_ACCESS_PRIV	This attribute specifies the address modifier to be used in high-level access operations, such as viInXX and viMoveInXX, when reading from the source.
VI_ATTR_SRC_BYTE_ORDER	This attribute specifies the byte order to be used in high-level access operations, such as viInXX and viMoveInXX, when reading from the source.
VI_ATTR_VXI_LA	Logical address of the local controller.
VI_ATTR_WIN_ACCESS_PRIV	This attribute specifies the address modifier to be used in low-level access operations, such as viMapAddress, viPeekXX and viPokeXX, when accessing the mapped window.
GPIB-VXI Specific MEMACC Resource Attributes
VI_ATTR_GPIB_PRIMARY_ADDR	Primary address of the GPIB-VXI controller used by the given session.
VI_ATTR_GPIB_SECONDARY_ADDR	Secondary address of the GPIB-VXI controller used by the given session.
VI_ATTR_INTF_PARENT_NUM	Board number of the GPIB board to which the GPIB-VXI is attached.

MEMACC Resource Events

This resource defines the following event for communication with applications, where AP = Access Privilege.

VI_EVENT_IO_COMPLETION - Notification that an asynchronous operation has completed.

Event Attribute	Attribute Value	Description	AP	Data Type	Range
VI_ATTR_BUFFER	0x3FFF4027UL	Address of a buffer that was used in an asynchronous operation.	RO	ViBuf	N/A
VI_ATTR_EVENT_TYPE	0x3FFF4010UL	Unique logical identifier of the event.	RO	ViEventType	VI_EVENT_IO_COMPLETION
VI_ATTR_JOB_ID	0x3FFF4006UL	Job ID of the asynchronous operation that has completed.	RO	iJobId	N/A
VI_ATTR_OPER_NAME	0xBFFF4042UL	Name of the operation generating the event.	RO	iString	N/A
VI_ATTR_STATUS	0x3FFF4025UL	Return code of the asynchronous I/O operation that has completed.	RO	iStatus	N/A
VI_ATTR_RET_COUNT	32-bit: 0x3FFF4026UL 64-bit: 0x3FFF4028UL	Actual number of elements that were asynchronously transferred.	RO	ViBus Size	*
VI_ATTR_RET_COUNT_32	0x3FFF4026UL	Actual number of elements that were asynchronously transferred.	RO	ViUInt32	0 to FFFFFFFFh
VI_ATTR_RET_COUNT_64**	0x3FFF4028UL	Actual number of elements that were asynchronously transferred.	RO	ViUInt64	0 to FFFFFFFF FFFFFFFFh

*The data type is defined in the appropriate VPP 4.3.x framework specification.

**Defined only for operating systems that are 64-bit native.

MEMACC Resource Operations

viIn8 (vi, space, offset, val8)

viIn16 (vi, space, offset, val16)

viIn32 (vi, space, offset, val32)

viIn64(vi, space, offset, val64)

 

viMapAddress (vi, mapSpace, mapBase, mapSize, access, suggested, address)

viMapAddressEx (vi, mapSpace, mapBase64, mapSize, access, suggested, address) 

viMemAlloc(vi, size, offset)

viMemFree(vi, offset)

viMemAllocEx(vi, size, offset64)

viMemFreeEx(vi, offset64)

 

viMove (vi, srcSpace, srcOffset, srcWidth, destSpace, destOffset, destWidth, length)

viMovEx(vi, srcSpace, srcOffset64, srcWidth, destSpace, destOffset64, destWidth, length) 

viMoveAsync (vi, srcSpace, srcOffset, srcWidth, destSpace, destOffset, destWidth, length, jobId)

viMoveAsyncEx (vi, srcSpace, srcOffset64, srcWidth, destSpace, destOffset64, destWidth, length, jobId)

 

viMoveIn8 (vi, space, offset, length, buf8)

viMoveIn16 (vi, space, offset, length, buf16)

viMoveIn32 (vi, space, offset, length, buf32)

viMoveIn64(vi, space, offset, length, buf64)

viMoveIn8Ex (vi, space, offset64, length, buf8)

viMoveIn16Ex (vi, space, offset64, length, buf16)

viMoveIn32Ex (vi, space, offset64, length, buf32)

viMoveIn64Ex(vi, space, offset64, length, buf64) 

viMoveOut8 (vi, space, offset, length, buf8)

viMoveOut16 (vi, space, offset, length, buf16)

viMoveOut32 (vi, space, offset, length, buf32)

viMoveOut64 (vi, space, offset, length, buf64)

viMoveOut8Ex (vi, space, offset64, length, buf8)

viMoveOut16Ex (vi, space, offset64, length, buf16)

viMoveOut32Ex (vi, space, offset64, length, buf32)

viMoveOut64Ex (vi, space, offset64, length, buf64) 

 

viOut8 (vi, space, offset, val8)

viOut16 (vi, space, offset, val16)

viOut32 (vi, space, offset, val32)

viOut64(vi, space, offset, val64)

 

viPeek8 (vi, addr, val8)

viPeek16 (vi, addr, val16)

viPeek32 (vi, addr, val32)

viPeek64(vi, addr, val64)

viPoke8 (vi, addr, val8)

viPoke16 (vi, addr, val16)

viPoke32 (vi, addr, val32)

viPoke64(vi, addr, val64)

 

viUnmapAddress (vi)