Agilent Technologies E2094S Podręcznik Użytkownika Pobierz pdf (Strona 94)

94 Agilent VISA User’s Guide

4 Programming via GPIB and VXI

Using Low-Level Memory Functions

Low-level memory functions allow direct access to memory on the

interface just as do high-level memory functions. However, with

low-level memory function calls, you must map a range of addresses

and directly access the registers with low-level memory functions, such

as viPeek32 and viPoke32.

There is more programming effort required when using low-level

memory functions. However, the program execution speed can increase.

Additionally, to increase program execution speed, the low-level

memory functions do not return error codes.

Programming the Registers

When using the low-level memory functions for direct register access,

you must first map a range of addresses using the viMapAddress

function. Next, you can send a series of peeks and pokes using the

viPeek and viPoke low-level memory functions. Then, you must free

the address window using the viUnmapAddress function. A process

you could use is:

1 Map memory space using viMapAddress.

2 Read and write to the register's contents using viPeek32 and

viPoke32.

3 Unmap the memory space using viUnmapAddress.

Low-Level Memory Functions

You can program the registers using low-level functions for 8-, 16-, or

32-bit transfers. This table summarizes the low-level memory functions.

Table 21 Summary of Low-Level Memory Functions

Function Description

viMapAddress(vi,

mapSpace, mapBase,

mapSize, access, suggested,

address);

Maps the specified memory space.

viPeek8(vi, addr, val8); Reads 8 bits of data from address specified.

1 2 ... 89 90 91 92 93 94 95 96 97 98 99 ... 145 146

Brak uwag

Agilent Technologies E2094S Podręcznik Użytkownika Strona 94