Chapter 2
Configuration and Startup Procedures
©
National Instruments Corporation
2-17
The RM then looks for
dynamic configuration devices
(
DC devices
) at
Logical Address 255 by asserting each MODID line and reading the
device’s ID Register. DC devices initially have a logical address of 255.
The RM
subsequently
assigns
each
DC
device
a different
logical
address.
For each DC device found, it not only reads the device’s configuration
registers as with SC devices, but also assigns each device the next unused
logical address by writing the appropriate value to the device’s Logical
Address Register. Using the nonvolatile configuration mode, you can set
the starting logical address for the RM to begin assigning DC devices.
Refer to Chapter 4,
, for more information on
nonvolatile configuration.
If any device has not passed its self-test, the RM forces that device offline
by setting the Sysfail Inhibit and Reset bits in that device’s Control
Register.
The RM then determines the address space of each device by reading its
ID Register. If the device’s address space is A16/A24 or A16/A32, the RM
allocates a section of A24 or A32 memory space to the device according to
the memory requirements indicated by the contents of its Device Type
Register and writes an appropriate value to the device’s Offset Register.
The RM configures the initial Commander/Servant hierarchy according to
each Commander’s Servant area size, using the algorithm described in the
VXIbus specification. The RM issues the appropriate
Read Servant Area
and
Device Grant
commands to each SC Commander. The RM retains all
devices not assigned to other Commanders as its immediate Servants.
Regardless of where DC device logical addresses are assigned, they are
never granted to an SC Commander. The DC Commander/Servant
hierarchy can be created in one of two ways:
•
All DC devices can be automatically assigned as Servants of Logical
Address 0 (the Resource Manager).
•
A custom hierarchy can be created through the use of the local
command set functions, as described in the
section of Chapter 3,
The RM then sends the
Read Protocols
query to all Message-Based
devices. The response to the query is saved internally for later use in
interrupt handler and GPIB configuration.
The RM configures the VXI interrupter and interrupt handlers using a
seven-entry table contained in nonvolatile configurations. During the
VXI interrupt configuration, the RM assigns interrupt levels to all
Programmable Handlers (PH) and Programmable Interrupters (PI).