IBM 1 Series - Socket Adapter Feature

Socket Adapter Feature
The socket adapter feature allows customer access to the Series/1 I/O
channel. The channel socket adapter is a two-component system to adapt
the 1-mm (0.040-in) IBM backpanel configuration to a 1.5-mm (0.060-in)
industry connector (see Figure 2-34). The first component is a 64-mm
(2.53-in) high IBM socket card (paddle card) with gold-plated,
printed-circuit tabs on the opposite end. The second component is a
modified 72-pin Continental* double billows feed-through connector to
allow customer access to 72 pins of the I/O channel. No logic electronics
are provided on the channel socket adapter; it is only a mechanical
adapter.
This assembly is plugged into any of the Series/1 I/O sockets. The
customer then plugs his 1.5-mm (0.060-in) printed circuit logic card into
the 72-pin connector. Dimensions for a customer printed circuit card,
which is designed to use the socket adapter feature, are shown in Figure
2-35.
The maximum amount of current a customer logic card may draw when
using the socket adapter feature is 3 amperes at +5 volts. Each customer
signal line directly connected to the Series/1 I/O channel must conform to
the electrical specifications described in ‘Processor I/O Channel Electrical
Characteristics” in this chapter. The ‘poll’ and ‘poll prime’ signals must be
propagated as described in ‘“‘Poll Sequence Description” in this chapter. As
viewed from the Continental-connector side of the socket adapter feature,
each customer signal line must have a characteristic impedance of between
60 and 120 ohms, and must present a nominal capacitive load, as
described in this section. The customer-supplied I/O channel drivers and
receivers must be located on the logic card (Figure 2-35) that connects
directly to the socket adapter.
The I/O channel is designed to support a nominal 30 pf per line per drop.
As discussed in ‘“‘Unit-Load Characteristics”’ in this chapter, TTL loads
may be substituted for general unit loads, resulting in an allowable
maximum of 60 pf for a single drop with TTL loads. The socket adapter is
assumed to be nominally 10 pf, yielding a customer-load maximum of 20
pf for a general load or 50 pf for a TTL load.
The signal lines available from the socket adapter are the same as for a
standard I/O channel, but with only four ‘request in bus’ lines,
corresponding to levels 0-3. The +5 volts dc is available on pin DO2.
Figure 2-36 contains the IBM backpanel-to-Continental-connector pin
assignment translation.
* Manufactured by Continental Connector Corporation
Processor I/O Channel 2-77