Motorola MCP750 Specifications download pdf (Page 70)

evice Driver Programming

5-6

Address Modiﬁers 5

For each data transfer on the VME bus, the bus master (either a processor or an I/O device)

must identify the characteristics of the data transfer by sending a special six-bit code along

with the transfer. This code is called an address modifier. For each different type of data

transfer there is one unique address modifier value to be used. The address modifier

speciﬁes:

• Address type (short, standard, extended)

• Access method (single location or multiple locations)

• Data access privilege (supervisory or non-privileged).

If the transfer originates with the processor, the VME I/O interface generates the

appropriate address modifier. If the device initiates the transfer, the device controller

generates the address modifier. In some devices, the address modifier is hard-wired into

the device controller; in others, jumpers or switches on the device set it. Alternatively,

some devices have programmable address modifiers. Refer to the installation manual that

accompanies the device for the procedure to conﬁgure the address modiﬁer.

The VMEbus standard speciﬁcation contains additional information on address modiﬁers.

VME Address Ranges 5

This section details the address ranges VME devices use on the VME primary I/O bus as

bus masters or slaves.

Unlike the PowerMAXION (Night Hawk), Power Hawk 610 processor and VME

addresses differ. The various busses and bridge chips between the processor and the VME-

bus map and translate the addresses, as this section describes.

VME Devices as VME Bus Slaves 5

When a processor acts as bus master on the VME bus and addresses VME devices on the

VME I/O bus, the VME devices are slave devices. The combination of the Power Hawk

610 and PowerMAX OS provides a highly conﬁgurable addressing arrangement for VME

slave accesses. Processor addresses from 0xC1000000 to 0xF0000000 in 64 Kb sections

can map to VME addresses above 0x80000000 with some exceptions and limitations.

The Motorola document MVME1604 Single Board Computer Programmer’s Reference

Guide provides more details on the hardware map registers. config(1m) explains

details on conﬁguring VME mappings via the PowerMAX OS.

Table 5-1: shows the address ranges for VME slave accesses.

1 2 ... 65 66 67 68 69 70 71 72 73 74 75 ... 343 344

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Motorola MCP750 Specifications Page 70