tifJLJ.J. I, 150.2 IBM VM/370 Planninq and System Generation Guide

RCTLUNIT Macro Use the RCTLUNIT macro to generate a real control unit block (RCUBLOK). One RCTLUNIT macro must be specified for each real control unit. The
maximum number of real control units is 511, providing you have enough
real storage to hold the real control unit blocks (RCUBLOKs). Control units generally fall into two categories: those supporting eight or
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 018 through 01F are mapped to a
control unit with address 018. On a multiplexer channel, several device addresses may fall within the address range of one BCTLUNIT macro. When this occurs, only one RCTLUNIT macro may be coded, eVEn though more than one real control unit
is present. This case is an exception to the general rule that one RCTLUNIT macro must be specified for each real control unit. For
example, a system console at address 009, a 2540 reader at address OOC and a 2540 punch at address OOD would be defined in a single RCTLUNIT macro with a control unit address of 008, even though the system console
and the 2540 card reader punch have different real control units. In
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 ReTLUNIT macros.
For control units supporting a range of more than eiqht device
addresses, use the FEATURE= operand. The base ad dress must be divisible
by sixteen. All devices from the base address up to the number of
devices specified by the FEATURE= operand are mapped to the specified
control unit. When a control unit has the hardware feature that allows
it to support more than eight devices, the RCTLUNIT macro must specify FEATURE=xxx-DEVICE, where xxx is the number of addressable devices that
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 3830 control unit with the 64-device
feature installed, you must specify FEATURE=64-DEVICE for it, even if
fewer than sixty-four 3330s are installed. VM/370 requires that all devices on one physical control unit be
specified on a single RCTLUNIT macro. The microcode in the 3830-2 which
supports 3350 DASD allows address skipping (in blocks of eight
addresses) on the same physical control unit.
Device Addresses 150-157 and 160-167 on first 3830-2 Device Addresses 158-15F and 168-16F on second 3830-2 This address scheme is not supported by Cr. All addresses on a given physical control unit must be specified with a single RCTLUNIT macro and
use the FEATUBE=xxx-DEVICE operand, where appropriate, for a contiguous
ranqe of addresses.
A device that attaches directly to the channel without a separate
control unit must still have a RCTLUNIT macro coded for it. For
example, if a 3210 is defined with an RDEVICE macro, it must have a
corresponding RCTLUNIT macro. Part 2. Defining Your VM/370 System 151