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VxWorks

Hardware Considerations Guide, 6.0

VMEbus Interrupts

Although VxWorks does not require VMEbus interrupts, it is a good idea to

support all VMEbus interrupts, especially if off-board Ethernet capability is

required. It may be possible to jumper the enabling and disabling of these

interrupts, but software control is preferable. Allowing software to read the

interrupt state is valuable.

VMEbus Interrupt Acknowledge

VMEbus interrupt requests must be acknowledged by the receiver. While some

implementers have chosen to force the ISR to acknowledge the interrupt, the more

elegant and preferred solution is to have the hardware automatically acknowledge

the request and present the CPU with the correct vector.

Software interrupt acknowledgment is not recommended because it carries a

significant performance penalty.

VME interrupt generation capability is also desirable. This is especially true if the

board is used in a backplane network with boards that do not have mailbox

interrupts. The most important example of this is on a backplane with a Sun board

running SunOS; if VME interrupt generation capability is not provided by the

slave, the backplane driver on the SunOS side needs to poll.

Power Usage

The VMEbus standard specifies the maximum power draw per voltage level.

Designers must adhere to these restrictions or clearly document additional power

requirements.

The typical maximum power consumption per board is about 7 watts. Boards that

have requirements in excess of this should emphasize it.

Extractors

VME boards should have card extractors mounted on the front panel.

VLSI Chips

A number of VLSI chips exist that offer complete VMEbus interface functionality.

Busless

When confronted with the task of porting VxWorks to a single-board computer,

Wind River strongly recommends the use of a visionICE or other JTAG debugger,

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RAM 6.0 BUX II Series Guia do Utilizador Página 18