Dpc Adapter Design Considerations; Application Notes - IBM 1 Series Manual

DPC Adapter Design Considerations
Application Notes
6-22 GA34-0033
The DPC adapter feature is used in applications that require access to the
processor I/O channel; it does not provide cycle-steal capability.
Therefore, the feature is limited to direct program control applications.
The overhead attributable to the DPC adapter, given that all user-device
delays on the DPC interface are 0, is 2.5 microseconds (maximum) added
to the execution time of the operate I/O instruction.
Recommended:
Input driver: TTL open collector (SN75451 or equivalent)
Requirement: Downlevel: +0.6 volt at 42mA, maximum;
minimum current required at down level, 42 mA at
+0.6 volt
Input terminators: 150-ohm and 300-ohm divider network to
+5 Vde +10%; effective termination impedance
equals 100 ohms
Note: Because this interface is nonisolated, it is important to ensure that
there is a good ground connection between the OEM device being
attached and the card file that contains the DPC adapter feature card. If
there is not a good ground connection, a large common-modevoltage may
be developed, and damage to the device or feature card could result.
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 DPC adapter should be connected to a device with a maximum 6.1-m
(20-ft) twisted-pair cable. Attachments to the top-card connector must use
a polarized Berg housing, part number 65405-013 (or equivalent); Berg
contact, part number 75598-003 (or equivalent); and #24 AWG wire.
The cable to the customer access panel feature can be made by using a
160-pin male connector block, Amp part number 202799-2 (or
equivalent); female contact, Amp part number 66108-1 (or equivalent);
and #24 AWGwire.
The DPC adapter card connector pin assignment for ground points should
be followed at the device end of the cable.
Diagnostic wrap capability is provided at all the DPC adapter feature
connection points for devices.