IBM 1 Series - Integrated Digital I;O Design Considerations; Application Notes

Integrated Digital I/O Design Considerations
Application Notes
5-18 GA34-0033
All integrated digital I/O points are nonisolated. The ground reference for
all these points is the top-card connector of the feature card. User-supplied
cables that are appropriate to the environment should be used and, in most
cases, should be shielded.
When attaching to the customer access panel, the shields of the input pairs
should be attached to the frame at the 160-pin connector through a short,
low-impedance stub. A screw terminal is provided for this purpose just
below and to the right of the connectors.
When attaching directly to the top-card connectors with a customer cable,
the shield of each cable should be attached to the frame as it enters the
processor, the I/O expansion unit, or the IBM 4997 Rack Enclosure,
whichever comes first. There are common pins provided for the reference
half of each signal pair on the top-card connectors. The reference halves
should be doubled-up and attached to these ‘“‘common”’ pins. The
reference lines must be doubled-up because there are not enough commons
to supply one pin per signal pair. After all the reference halves are
connected, there should be at least six empty common pins. The empty
pins should be joined together and attached to the frame ground through
as short a path as possible. Screw terminals for this purpose are located on
top of the processor and I/O expansion units. The empty pins should be
located in a group at the very top of the card.
Because the performance of this interface may be affected by noise,
appropriate arc suppression, noise filtering, etc., may be necessary on the
user’s inputs.
The cables that plug into the top-card connector on the integrated digital
I/O feature card should be made using #24 AWG wire and must use Berg
part number 75598-003 pins (or equivalent) and Berg part number
65405-013 housing (or equivalent). Refer to Figure 5-6 for an illustration
of the cable connector.
The cable to the customer access panel can be made using a 160-pin male
connector block, Amp* part number 202799-2 (or equivalent): female
contacts, Amp part number 66108-1 (or equivalent); and #26 AWG wire.
* Amp, Incorporated