maximum number of real control units is 511, providing you have enough
real storage to hold the real control unit blocks
fewer devices, and those supporting more than eight devices.
A control unit that supports eight or fewer devices must be assigned
an address that is divisible by eight. All devices with an address
equal to the control unit's address (the base address) or any of the
next seven sequential addresses are mapped to this control unit. For
example, devices with addresses of
control unit with address
is present. This case is an exception to the general rule that one
example, a system console at address
and the
this case, any valid control unit type can be coded. The only exception
to this is that control units that operate on a shared subchannel must
be specified by separate
For control units supporting a range of more than eiqht device
addresses, use the
by sixteen. All devices from the base address up to the number of
devices specified by the
control unit.
it to support more than eight devices, the
can be attached to this control unit. The number of devices specified
must be divisible by sixteen and rounded to the next higher increment of
sixteen if not divisible. The maximum number of devices that can be
attached to a control unit is 256.
For example, if you have a
feature installed, you must specify
fewer than sixty-four
specified on a single
supports
addresses) on the same physical control unit.
Device Addresses
use the
ranqe of addresses.
A device that attaches directly to the channel without a separate
control unit must still have a
example, if a
corresponding