Specifications

Series 6000 Hardware Environmen

4-5

Transfer Width Support 4

For all non-block mode transfers, (H)VME supports byte, word and long-word addresses.

It supports byte addresses on even and odd addresses. It supports word addresses (16-bit)

on even addresses. It supports longword transfers on longword addresses.

Synchronous Block Transfers or VME Block Mode Transfers (BMT) only support long-

word addresses.

Address Types 4

Bus masters on the (H)VME I/O bus can use different types of addresses dynamically:

short (16 bit-address), standard (24-bit addresses), or extended (32-bit addresses).

The source of the addresses can either reside on the local (H)VME bus or come from the

processor acting as bus master.

Short address accesses come from sources local to the (H)VME I/O bus on which they

originate, and cannot go outside of the local bus. Standard addresses can access either sys-

tem memory (below 12MB) or memory local to the (H)VME bus. Extended addresses

access all of system memory.

Address Modiﬁers 4

For each data transfer on the (H)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. Different types of

data transfers use speciﬁc address modiﬁer values. 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 (H)VME I/O interface generates the

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

erates 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 HN6200 or HN6800 Architecture Manuals contain additional information on address

modiﬁers.