Motorola MVME2400 Series Service Manual download pdf (Page 280)

4-4 Computer Group Literature Center Web Site

Universe II (VMEbus to PCI) Chip

VMEbus Interface

Universe II as VMEbus Slave

The Universe II VME Slave Channel accepts all of the addressing and data

transfer modes documented in the VME64 specification (except A64 and

those intended to support 3U applications, i.e. A40 and MD32). Incoming

write transactions from the VMEbus may be treated as either coupled or

posted, depending upon the programming of the VMEbus slave image.

(Refer to VME Slave Images in the Universe II User Manual.) With posted

write transactions, data is written to a Posted Write Receive FIFO

(RXFIFO), and the VMEbus master receives data acknowledgment from

the Universe II. Write data is transferred to the PCI resource from the

RXFIFO without the involvement of the initiating VMEbus master (Refer

to Posted Writes in the Universe II User Manual for a full explanation of

this operation.). With a coupled cycle, the VMEbus master only receives

data acknowledgment when the transaction is complete on the PCI bus.

This means that the VMEbus is unavailable to other masters while the PCI

bus transaction is executed.

Read transactions may be prefetched or coupled. If enabled by the user, a

prefetched read is initiated when a VMEbus master requests a block read

transaction (BLT or MBLT) and this mode is enabled. When the Universe

II receives the block read request, it begins to fill its Read Data FIFO

(RDFIFO) using burst transactions from the PCI resource. The initiating

VMEbus master then acquires its block read data from the RDFIFO rather

than from the PCI resources directly.

Universe II as VMEbus Master

The Universe II becomes VMEbus master when the VME Master Interface

is internally requested by the PCI Bus Slave Channel, the DMA Channel,

or the Interrupt Channel. The Interrupt Channel always has priority over

the other two channels. Several mechanisms are available to configure the

relative priority that the PCI Bus Slave Channel and DMA Channel have

over ownership of the VMEbus Master Interface.

The Universe II’s VME Master Interface generates all of the addressing

and data transfer modes documented in the VME64 specification (except

A64 and those intended to support 3U applications, i.e. A40 and MD32).

1 2 ... 275 276 277 278 279 280 281 282 283 284 285 ... 353 354

No comments

Motorola MVME2400 Series Service Manual Page 280