The past 20 years the VMEbus has reached a dominant position for industrial
busses with a number of suppliers.
Despite numerous new bus systems based on the rapid changes in chip
technology, VMEbus systems offer significant advantages such as their
robustness, reliability and increased availability of processor, memory
and I/O cards.
Additional advantages appear under real-time
conditions, where unforeseen events have to be managed. This is realised
with the program interrupt concept and variable control that closely monitors
the bus system.
With the increase in processing speeds and data transmission rates,
3 row DIN 41 612 connectors have reached their limit, so the VME standard
needs to be enhanced further.
When VME architecture was increased from 8-bit to 64-bit and data transmission
rates up to 160 Mbyte/s (VME 64x), HARTING introduced har-bus®
64 with 160 pins. This Eurocard connector is 100% backwards compatible
to existing 3 row connectors with 96 contacts, therefore old can plug
into new.
To offer the best design possible from the start, HARTING developed
spice models that were later certified via signal integrity measurements
of the connector.
High precision slot
structure with VME pinning for connector characterisation.
System
description
Backward compatibility
The design of har-bus® 64 female
connectors allows mating of any combinations of the 5 or 3 row versions
without mechanical interference, this making it possible for users to
upgrade and maintain existing systems at lower costs. It is also possible
to mate 5 row male connectors with 3 row female connectors.
The feature of backward compatibility allows
a gradual upgrade of existing Eurocard based systems without the additional
cost of a complete system redesign. It is not necessary to replace conventional
96 pin based boards as they remain pluggable into the 160 pin based systems.
Not only VMEbus, but also existing proprietary bus systems for which
3 row 96 pin connectors are no longer performance sufficient,
har-bus® 64 provides the opportunity to adapt the system economically
without a complete redesign to a new bus architecture.
har-bus® 64 - five rows – 160 poles
Two additional rows of contacts in the har-bus®
64 connector offer new system features:
Additional contacts
for I/O and system upgrade
New voltage supplies
for 3.3 V and 48 V system components
Identifying locations
of system components and the bus length. “Plug & Play“
Improved signal/ground
ratio for reliable signal data transfer at rates up to 320 MByte/s
Live Insertion for replacing
processor or memory cards without closing down the system
User defined pins for test and maintenance bus lines
The advantages of har-bus®
64 in detail
User-defined pins in the outer rows can be used for application specific
functions such as additional I/O.
Configured as a shield to provide larger ground return paths, they assure
for data transfer rates up to 320 MByte/s.
Proprietary bus systems can utilise the new contact rows to optimise
signal-to-ground ratios and improve system speed.
Four preleading
contacts (1.5 mm) serve to pre-load the transmit and receive logic
so that the bus will not experience glitches during live
insertion of new cards into the backplane.
Backplane connector terminations are designed in solderless
press-in technology.
The connector can be installed without any special tooling using economical
flat dies for high speed insertion.
The insulator, made of LCP, has an inherent flammability rating of UL
94-V0 and therefore provides an environment
friendly connector. In addition, the heat deformation stability
of LCP makes the connector surface-mount
compatible.
Partially
gold plated terminations with precisely formed tips serve as contact
area for rear transition boards.
har-bus® 64system description
System description har-bus®
64 with switches
As
a typical multiprocessor bus, VME has to distribute processor information
continuously according to the right priorities.
This is done through the
well known daisy-chain
lines.
The VME protocol requests
5 daisy-chains on
position 1 of every backplane.
These lines are defined
to go through every
daughter card.
Therefore, in case of
unloaded card slots
the signal have to be bridged across the connector.
Bridging variants:
1. The empty card slots may be assembled with dummy cards, that bridge
the daisy-chain lines.
2. Bridging can be achieved by inserting 5 jumpers on the backplane
manually.
3. Bridging by using IC's with internal integration OR the function
may accept automatic daisychaining.
4. The 5-row har-bus®
64 connector with switches allows an automatic switching. In the
case of an unmated daughter card the connector bridges the signals at
positions a21-22, b4-5, b6-7, b8-9 and b10-11. The switch elements open
automatically when the daughter card is mated, so that the daughter card
accepts the ongoing signal daisy-chain.
Advantages:
Passive
backplane; no active components assembled
No
additional space required, due to integrated switching function inside
the connector
No
jumpers on the backplane
User
friendly regarding maintenance and repairing
Automatically
daisy-chaining through mating/unmating the daughter card
The current carrying capacity is limited by
maximum temperature of materials for inserts and contacts including terminals.
The current capacity curve is valid for continuous, non interrupted current
loaded contacts of connectors when simultaneous power on all contacts
is given, without exceeding the maximum temperature.
Control and test procedures according to DIN
IEC 60 512
With selective loading higher currents can
be transmitted. The requirements according to VITA 1.7 are fulfilled.
har-bus®
64 with switches
Deviating technical characteristics for the
switching elements.
