IBM Series 1 User Manual page 17

timing condition. (Timeout conditions for error detection
are, of course, not excluded.) An asynchronous channel
allows the attachment of devices that have various speeds
and technologies over a wide range of distances or delays.
All of the I/O channel signal lines are TTL level
compatible. This allows the user to attach a wide variety
of I/O devices.
The I/O channel signal lines are distributed internally
through the processor backpanel board to each I/O attachment
card socket. Distribution of the channel signal lines can
be continued
by
connecting cables or a channel repower
feature from a processor I/O socket (usually the A-socket)
to an adjacent I/O expansion unit as the particular
processor or configuration requires. A channel repower
feature card is required if the channel is extended from an
1/0
expansion unit to an additional I/O expansion unit.
IBM I/O attachment cards plug directly into the
backpanel sockets. External I/O devices are connected to
the attachment cards via top-card connectors.
Two features are available for connecting non-IBM
devices directly to the channel: (1) the channel socket
adapter feature and (2) the channel repower featur~.
•
Channel socket adapter feature -- this feature consists
of an
IBM
printed circuit card that plugs into the
backpanel of the processor unit or I/O expansion unit.
An industry standard connector on the top edge of the
IBM printed circuit card accepts the userts I/O adapter
card. For further information, see "Socket Adapter
Featu['e" near the end of this chapter.
• Channel repower feature -- this feature is a logic card
that repowers and isolates the channel signal lines.
This card can be installed in any I/O socket, as the
last series element on the channel, to provide for
connection of additional I/O adapters or controllers.
For further information, see "Channel Repower Feature"
near the end of this chapter.
If the user connects directly to the channel at the
backpanel sockets instead of through one of the available
features, unit load, power, and physical requirements must
be considered. These and other requirements are discussed
in subsequent sections of this chapter.
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