Second-Generation Channel Interface Processor (CIP2) Installation and Configuration 11
What Is the CIP2
Note the switch marked S (for select mode) and B (for bypass mode). The switch is located on the
rear of the PCA connector. (See Figure 6.) The select/bypass switch is required to allow the cable to
be separated from the PCA without “opening” the select-out loop.
Caution
To prevent halting the system or negatively affecting the mainframe operating system,
verify that the select/bypass switch is in bypass mode before you remove the PCA connector from
the CIP2.
Figure 6
Select/Bypass Switch on the Rear of the PCA Connector (CAB-PCA-Y Bypass Shown)
In select mode the PCA is operational, and the select-out signal is passed in a loop to all control lines
on the channel. All control units have a relay that shorts the incoming select-out signal to the
outgoing select-out signal when power is not applied to the control unit. When power is applied, the
relay is opened, and the signal is passed to the PCA.
Without the select/bypass switch in bypass mode, the channel would need to be taken offline before
servicing or replacing a CIP2. If the selected address does not match, the select-out signal is passed
to the next control unit. If the select-out signal gets all the way back to the channel, the control unit
being addressed is not present.
Note
In bypass mode, the incoming select-out signal is shorted to the outgoing select-out signal,
bypassing the PCA and allowing other devices on the channel to function properly.
Caution
Make sure you provide adequate strain relief for the heavy bus and tag cables that attach
to the PCA, to prevent damaging the PCA connector on the CIP2 by unintentionally disconnecting
the Y cable from the PCA connector.
VA and VB Cables
The two bus and tag cables with connector blocks have a DB-78 (male or female) connector on the
CIP2 end and 48-pin type-A connector blocks on the bus and tag ends. (See Figure 7.) VA and VB
cables are 56 inches (1.42 meters) in length.
For the bus and tag cable that attaches between the host and the PCA, the model number is
CAB-PCA-VA, and it is referred to as the VA cable. The female 78-pin connector might be labeled
IN and is typically light gray. The cable labeled P2 is bus, and the cable labeled P3 is tag. Looking
into the end of the female 78-pin connector (on the VA cable), with the wide part of the connector
D-shell on top, the P2 (bus) cable is on the right, and the P3 (tag) cable is on the left. The plastic on
the ends of the bus and tag connectors might be black or dark gray.
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