User`s guide

108 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 26 Summary of Low-Level Memory Functions
Function Description