1.-6. Exceptions with the same priority as the priority of program­
interruption conditions for the general case.
7.A Access exceptions for second instruction halfword.
7.B.l Operation exception if the dual-address-space facility is not
installed.
7.B.2 Special-operation exception due to OAT being off, the CPU being in secondary-space mode, or the subsystem-linkage­
control bit in control register 5 being zero.
8.A Trace exceptions.
8.B.l Privileged-operation exception due to attempt to set the
supervisor state when in the problem state.
8.B.2 Specification exception due to nonzero value in bits 0-7 of
general register R
2
8.B.3 Special-operation exception due to the ASN-translation con­
trol, bit 12 of control register 14, being zero (PT-ss only).
8.B.4 ASN-translation exceptions (PT-ss only).
8.B.5 Primary-authority exception due to authority-table entry
being outside table (PT-55 only).
8.B.6 Addressing exception for access to authority-table entry
(PT-ss only).
8.B.7 Primary-authority exception due to P bit in authority-table
entry being zero (PT-ss only).
9. Space-switch event (PT-ss on!y).
Priority of Execution: PROGRAM TRANSFER
Programming Notes
1. The operation of PROGRAM TRANSFER
(PT) is such that it may be used to
restore the CPU to the state saved
by a previous PROGRAM CALL. This
restoration is accomp!ished by
issuing PT 3,14. Though general
registers 3 and 14 are not restored
to their original values, the PASN,
PSW-key mask, problem-state bit,
and instruction address are
restored, and the authorization
index, PSTD, and LTD are made
consistent with the restored PASN.
2. With proper authority, and while
executing in a common area, PROGRAM
TRANSFER may be used to change the
primary address space to any
desired space. The secondary
address space is also changed to be
the same as the new primary address
space. 3. Unlike the RR-format branch in­
structions, a value of zero in the R2 field for PROGRAM TRANSFER
designates genera! register 0, and
branching occurs. Chapter 10. Control Instructions 10-33
PROGRAM TRANSFER
Instruction
'B228' 1////IRtIR21 __ I I IA 10-34 System/370 Principles of Operation
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