Chapter 4
Programming
4-2
©
National Instruments Corporation
Plug and Play Initialization
The AT E Series boards are fully compatible with the Intel Plug and Play
Specification version 1.0. The Plug and Play system arbitrates and assigns
resources through software, freeing the user from manually setting
switches and jumpers. The bus-related resources must be configured before
attempting to execute a register level program. Both the bus-related and
data acquisition-related Plug and Play configurations are described in the
AT-MIO/AI E Series User Manual.
If your system has a Plug and Play configuration manager which assigns
available resources at startup, you must query the configuration manager to
determine the resources assigned to each board. If no configuration
manager is installed, then a configuration program is necessary to assign
resources to the board. The AT E Series Register-Level Programmer
Manual Companion Disk contains a function that a user can execute to
configure the base address of the AT E Series board. It is very important to
note that the given Plug and Play initialization only applies for one board.
If more than one board needs to be configured, the Plug and Play
specification explains the procedure.
The software impementation of the full Plug and Play protocol is beyond
the scope of this manual, and is discussed in the ISA Plug and Play
Specification version 1.0 available from Intel. This section discusses how
to assign a base I/O address to an AT E Series board. All access to the
Plug and Play registers is performed through three I/O address locations.
The Address Port is at location 0x279, and is used to indicate which
configuration register is the target of the next data transfer. The Write Data
Port is at location 0xA79, and is used to write to the configuration register
indicated by the Address Port contents. The Read Data Port is moveable in
the range of 0x203 to 0x3FF, and is used to read the configuration register
indicated by the Address Port contents. The location of the Read Data Port
is set by writing to certain configuration registers.
Access to the Plug and Play configuration registers is controlled by an
internal state machine. The state machine consists of four states: Wait4Key,
Sleep, Isolation, and Configuration. The board powers up in the Wait4Key
state, where the board is inactive and not yet configured. A sequence of
specific accesses to the Address Port will move the board into the Sleep
state. This long sequence of 34 writes was chosen to decrease the chances
that a poorly written program that writes randomly into I/O space does not
accidentally access the Plug and Play configuration registers. The function
Write_PNP_Initiation_Key
performs this series of writes.
Содержание AT-AI-16XE-10
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