Microsoft Office Pro Plus Understanding the VXI VM

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from an engineer Understanding the VXI/VME Interrupt and Signal Acknowledge Cycle
The VME bus specification defines the Priority Interrupt Bus to ensure that a VME gadget can
asynchronously request support from a controller. This offers a VME/VXI device a way of acquiring
the controller’s attention at any time.
A VXI/VME bus method has 7 interrupt lines physically linked to all slots from the chassis.
This document addresses interrupts on equally VME and VXI programs.
Interrupt line 7 has the greatest priority, and interrupt line 1 has the lowest priority.
In addition to your true interrupt lines, the Priority Interrupt Bus also consists of a
daisy-chained interrupt acknowledge signal and areas of the Information Transfer Bus
(the knowledge lines, the data acknowledge line,Office 2010 Keygen, and also the reduced 3 deal with lines).
The table beneath summarizes each and every signal used in the Priority Interrupt Bus and
summarizes the perform of each signal. A device that requests support by asserting
one of the interrupt lines is known as an interrupter. A purposeful gadget referred to as
an interrupt handler companies the interrupt. There might be a lot more than 1
interrupt handler in a VXI/VMEbus system. National Instruments embedded controllers
and external MXI bus controllers let you configure multiple interrupt handlers
(from one to 7).
Table I. Priority Interrupt Bus Signals

Signal
Function
IRQ1*-IRQ7*
An interrupter uses this signal to indicate that it is requesting support.
IACK*
An interrupt handler uses this signal to indicate that it has received an interrupt and is ready to receive a status/ID that will tell the handler how to proceed with servicing the interrupt.
IACKIN*/
IACKOUT*
A module receives the IACK* on IACKIN*. It places a status/ID on the bus if the interrupt level being serviced matches the module’s interrupt level and if the gadget is interrupting. Otherwise, the module passes the signal on using IACKOUT*.
A01-A03
The interrupt handler asserts these lines with the value corresponding to
the interrupt level being serviced.
D00-D31
The interrupter being serviced places the status/ID on these lines once IACK* has been received.
DTACK*
The interrupter uses this signal to indicate that its status/ID is asserted on the information lines.

A a lot more detailed explanation of what happens from the interrupt cycle is outlined beneath.
A device that requests service by asserting a single from the interrupt lines is known as an interrupter. A purposeful system generally known as an interrupt handler providers the interrupt. There may be more than one particular interrupt handler in a VXI/VME bus program. However, there can only be one particular interrupt handler per interrupt level from the technique. Countrywide Instruments embedded controllers and exterior MXI bus controllers allow you to configure multiple interrupt handlers (from a single to 7).
Therefore, two types of interrupt handler techniques are possible:
A single handler system A distributed system
In a single handler method, one particular interrupt handler device providers all interrupt lines. Inside a distributed method, there are two or much more handlers,Office 2010 Activation Key, every single servicing an exclusive subset with the 7 interrupt lines. Most methods are single handler methods, where the technique controller handles all interrupt lines within the chassis. It is possible for VXI devices to act as programmable interrupt handlers, but this is not very common. The Useful resource manager detects programmable VXI interrupt handlers and uses information stored within the device’s configuration registers to assign the interrupt levels that will be handled by the VXI gadget. Note that VME devices do not define a standard set of configuration registers - you must use Test and Measurement Explorer or VXI Edit/vxitedit to enter any configuration information associated with the VME system.
There are two types of interrupters:
Release On ACKnowledge (ROAK) Release On Register Access (RORA)
Most VXI and VME instruments fall under the ROAK category along with the sequence of events described under is only applicable to ROAK devices.
The Sequence of Events During an Interrupt (IACK*) Cycle
After a gadget asserts an interrupt, it waits for a response from the interrupt handler. When the interrupt handler detects that an interrupt line has been asserted, the interrupt handler asserts the IACK* (interrupt acknowledge) signal. It also sets the decrease 3 address lines A01 – A03 to indicate which interrupt line it is trying to acknowledge with the IACK* signal. The IACK* line that the handler drives is connected for the IACKIN* pin of slot 0 from the chassis (Slot one in VME bus techniques). If the module inside the first slot is not asserting the interrupt line being acknowledged, the module must propagate the IACK* signal to its IACKOUT* pin, which is related towards the next slot’s IACKIN* pin. The propagation from the IACK* signal from slot to slot continues until the IACK* signal reaches the first module that is interrupting on the line being acknowledged. When the interrupter sees IACK*, it places its status/ID on the data/bus.
The interrupt handler reads the status/ID. Because the interrupt lines are open collector lines, a lot more than one system can assert the same interrupt line at the same time. Therefore, the module asserting the interrupt does not propagate the IACK* signal. This action prevents other devices that are interrupting on the same line from acquiring the IACK* signal and attempting to respond at the same time. After the interrupt handler providers the interrupter, the interrupter releases the line. If other devices are interrupting on the same line, the handler then begins another interrupt acknowledge cycle to services the next interrupter on that line. The following figure illustrates the interrupt acknowledge daisy-chain.
Figure one. Interrupt Acknowledge Daisy-Chain
Note: RORA devices require you to read/write a system distinct register in order to complete the interrupt acknowledge cycle.
In this figure, the gadget in slot 4 has asserted an interrupt. The figure shows that if more than one particular gadget asserts the same interrupt line,Microsoft Office Pro Plus, the device closest to slot 0 (slot 1 in VME) has the highest priority for interrupt service because it receives the IACK* signal first. The next closest device has the next greatest priority, and so on. It is important to remember that the IACK daisy chain must be linked across unoccupied backplane slots, or else interrupts coming from devices to your right of the empty slot will not be acknowledged. Most chassis have jumperless backplanes where this daisy-chain connection happens automatically. However,Office 2007 Pro Key, on older backplanes that are jumpered, jumpers must be utilised to connect the IACK daisy chain across unoccupied slots. On jumpered backplanes, you should also pull the jumpers from the occupied slots to ensure the IACK daisy-chain is not mistakenly connected through the slot containing the interrupter.

Status/ID Value
The status/ID in most VME systems is an 8-bit value. In VXI programs, the status/ID is either a 16-bit or 32-bit status/ID value. Message-Based devices that have interrupter capability must return at least a 16-bit status/ID with an optional 32-bit value. Currently, 32-bit status/IDs are uncommon. In VME techniques, the status/ID is usually a vector. The processor uses this vector to calculate an deal with to a position in an interrupt jump table. The entry in that table is the deal with with the start from the interrupt support routine.
Therefore, when the processor handles the interrupt and receives the status/ID, it jumps directly to your beginning from the interrupt services routine and executes the interrupt support routine code. The system integrator installs the interrupt support routine at the memory location that the jump table specifies.
In VXI techniques (and all Nationwide Instruments VXI/VME Controllers), the status/ID is no longer a
vector. It is de-coupled from the processor operation. After the interrupt handler receives the
status/ID, controller software invokes the appropriate support subroutine and passes the
status/ID value to your subroutine.
The general format of the status/ID for a Register-Based VXI system is shown
within the following table.
Table II. General Status/ID Format for VXI Bus Devices

Bits
31-16
15-8
7-0
Contents
Device-Dependent
Cause/Status
(Device-Dependent)
Logical Address
of Interrupter
For Message-Based VXI devices, there is a further definition from the status/ID format. The status/ID can take on either a Response format or an Event format. Under the Event Format, bit 15 of your status/ID must be set. The values of status/ID bits 8 through 14 define the Event condition. The VXI bus specification currently defines these bits for 3 distinct events. It also defines a syntax for defining your own events. The events defined inside the VXI bus specification and their corresponding values for status/ID bits 8 through 15 are listed under.
No Cause Given (0xFF) - This event is sent by a Register-Based device that has only one reason to signal its Commander. Usually, this event is issued when an operation completes.
Request True (0xFD) — This event is sent by a gadget when the system requires service.
Request False (0xFC) — This event is sent by the device when the device no longer requires services. The VXI bus specification also defines a syntax for sending user-defined
events. This format specifies that bit 15 must be 1 and bit 14 must be 0. Bits 8 – 13 can then be utilised to specify a user-defined event,Windows 7 Professional Product Key, as shown within the following table.

Table III. Message-Based Device Status/ID—User-Defined Event Format

Bits
31-16
15
14
13-8
7-0
Contents
Device-Dependent
1
0
User-Defined Event
Logical Address
of Interrupter
Except for defining the decrease 8 bits of the status/ID value to be the logical deal with of the interrupter, the VXI bus specification defines only a few particular values of the status/ID. Usually, when you are working with a device capable of producing interrupts, you need to refer to the documentation accompanying the gadget to see what meaning, if any, the other bits of your status/ID have. Often, you control the conditions under which the interrupt is generated, along with the genuine status/ID is not important because you will know in advance why the system is sending interrupts.

Signals
Instead of asserting an interrupt line, some devices can request service by producing a signal. "Signal" in this context is not an electrical signal (such as the backplane signals discussed earlier inside the course), but rather a write of the 16-bit value to your signal register of another gadget. The signal register is simply a VXI configuration register that has a value written to it by another gadget capable of taking control of your bus. Not all devices implement a signal register. The term signal originates from its use in UNIX, where a signal is a means of inter-process communication. To use signals, the following two conditions must apply:
The signaling device must be able to take control of the VXI bus The gadget to which the signal is being sent must implement a signal register.
The signaling gadget uses the Knowledge Transfer Bus to write a 16-bit value for the signal register, which is located at offset 8 within the configuration registers for the device being signaled. The 16-bit value has exactly the same format as the 16-bit status/ID.
The procedure for handling a signal through software is the same as for an interrupt. The processes discussed above for signals along with the interrupt cycle happen completely on the hardware level. These processes are transparent to a user’s application. When a controller senses an interrupt or sees that its signal register has been written to, the controller generates a local processor interrupt that lets the software driver know the event has occurred.