The condition code is set to reflect the state of
thereference and change bits before the reference
bit is set to zero.
Resulting Condition Code:
o Reference bit zero, change bit zero
1 Reference bit zero, change bit one
2 Reference bit one, change bit zero
3 Reference bit one, change bit one
Program Exceptions:Operatilon (if the translation feature is not in
stalled)Privileged operation
Access (addressing for operand accessonly, oper
and 2)
Set Clock[S] C==._B2_04 __ __ D_2 o 16 20 31
Thecurrent value of the time-of -day clock is re
placed by the contents of the doubleword designated
by the second-operand address, and the clock is
placed in the stopped state.
The operand designated by the instruction is con
sidered an unsigned, 64-bit, fixed-point This operand replaces the contents of the clock, as
determined by the clock's resolution.Only those bits
of the operand are set in the clock that correspond
to the bit positions to be updated by the clock; the
contents of the remaining rightmost bit positions are
not preserved in the clock and are ignored.
After the clock value is set, the clock is placed in
the stopped state. The clock leaves the stopped state
to enter the set state and resume countingunder control of the time-of -day clock control bi1c (control register 0, bit 2). When the bit
is zero or the clock-synchronization facility is not
installed, the clock enters the set state at thecO!11ple tion of the instruction. When the bit is one, the
clock remains in the stopped state either until the bit
is set to zero or until any other running time-oI-day
clock in the configured system is incremented to a
value ofaU zeros in bit positions 32-63.
The value of the clock is changed, and the clock is
placed in the stopped state only if the TOD-clock
switch on the system console is in the enable-set
position. If the switch is in the secure position, the
value and the state of the clock are not changed. The
two results are distinguished by condition codes0 108 System/370 Principles of Operation
and 1, respectively. When the clock is not opera
tional, regardless of the setting of the TOD-clock
switch, the value and the state of the clock are not
changed, and condition code 3 is set.
The operand must be designated on a doubleword
boundary; otherwise, a specification exception is
recognized, and the operation is suppressed. Access
exceptions are recognized regardless of the state of
the clock and the setting of the TOD-clock switch.
Resulting Condition Code:
o Clock value set
1 Clock value secure
2 -
3 Clock not operational
Program Exceptions:
Privileged operation
Access (fetch, operand 2)
Specification
Set Clock ComparatorSCKC [S] B206 o 16 20 31
The current value of the clock comparator is re
placed by the contents of the doubleword designated
by the second-operand address.Only those bits of the operand are set in the clock
comparator that correspond to the bit positions to be
compared with the time-of -day clock; the contents
of the remaining rightmost bit positions are ignored
and are not preserved in the clock comparator.
The operandmust be designated on a doubleword
boundary; otherwise, a specification exception is
recognized, and the operation is suppressed. The
operation is suppressed on protection and addressing
exceptions.
Condition Code: The code remains unchanged.
Program Exceptions:
Operation (if the clock comparator is not in-
stalled)
Privileged operation
Access (fetch, operand 2)
Specification
the
bit is set to zero.
Resulting Condition Code:
o Reference bit zero, change bit zero
1 Reference bit zero, change bit one
2 Reference bit one, change bit zero
3 Reference bit one, change bit one
Program Exceptions:
stalled)
Access (addressing for operand access
and 2)
Set Clock
The
placed by the contents of the doubleword designated
by the second-operand address, and the clock is
placed in the stopped state.
The operand designated by the instruction is con
sidered an unsigned, 64-bit, fixed-point
determined by the clock's resolution.
of the operand are set in the clock that correspond
to the bit positions to be updated by the clock; the
contents of the remaining rightmost bit positions are
not preserved in the clock and are ignored.
After the clock value is set, the clock is placed in
the stopped state. The clock leaves the stopped state
to enter the set state and resume counting
is zero or the clock-synchronization facility is not
installed, the clock enters the set state at the
clock remains in the stopped state either until the bit
is set to zero or until any other running time-oI-day
clock in the configured system is incremented to a
value of
The value of the clock is changed, and the clock is
placed in the stopped state only if the TOD-clock
switch on the system console is in the enable-set
position. If the switch is in the secure position, the
value and the state of the clock are not changed. The
two results are distinguished by condition codes
and 1, respectively. When the clock is not opera
tional, regardless of the setting of the TOD-clock
switch, the value and the state of the clock are not
changed, and condition code 3 is set.
The operand must be designated on a doubleword
boundary; otherwise, a specification exception is
recognized, and the operation is suppressed. Access
exceptions are recognized regardless of the state of
the clock and the setting of the TOD-clock switch.
Resulting Condition Code:
o Clock value set
1 Clock value secure
2 -
3 Clock not operational
Program Exceptions:
Privileged operation
Access (fetch, operand 2)
Specification
Set Clock Comparator
The current value of the clock comparator is re
placed by the contents of the doubleword designated
by the second-operand address.
comparator that correspond to the bit positions to be
compared with the time-of -day clock; the contents
of the remaining rightmost bit positions are ignored
and are not preserved in the clock comparator.
The operand
boundary; otherwise, a specification exception is
recognized, and the operation is suppressed. The
operation is suppressed on protection and addressing
exceptions.
Condition Code: The code remains unchanged.
Program Exceptions:
Operation (if the clock comparator is not in-
stalled)
Privileged operation
Access (fetch, operand 2)
Specification