ADLINK Technology NuDAQ ACL-8454, Руководство пользователя

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Registers Format
3.6 Low-level Programming
To manipulate the ACL-8454, users may understand how to write a
hardware dependant low-level program. The low-level programming
can be carried out by using either assembly or high-level language
such as BASIC or C language. The following gives examples to
show how to use programming language to access an add-on I/O
card.
Getting Start
Before programming, the add-on card should be correctly installed.
After installing the card, the users should already understand how
much system (PC) resources are used by this card, such as I/O
address, IRQ channels, and even DMA channel, etc.
The second step is to study the register format and the operation
theorem of the card. Then users can try to write low-level programs
to operate it. Although the high-level program library is available, the
low-level programming can improve the efficiency and perform
functions which the library does not support. The low level
programming is not difficult and may be necessary to understand.
Programming Language
The programming language to be used is dependent on users'
familiarity and the system requirement. No matter what kind of
language is used, the user must understand the syntax of the I/O
instructions to access the I/O card. The following sections introduce
the syntax of the often used programming language. In each section,
the write (output) port instruction and the read (input) port instruction
are shown. In the examples, the base address of the I/O card is
assume as
HEX 240 and the port of the register to be access is
BASE+2.
Assembly
To write an output port:
out 240h,value
out 240h,register
To read an input port
in A, 240h