Cray CRAY-1 - Initiated by Dead Start Sequence; Initiated by Interrupt Flag Set; Initiated by Program Exit

exchange package has stopped. The same 16-word block of memory is used
as the source of the inactive exchange package and the destination of the
currently active exchange package. The location of this block is
specified by the content of the exchange address register and is a part of
the currently active exchange package. The exchange sequence may be
initiated in three different ways.
1. Dead start sequence
2. Interrupt flag set
3. Program exit
Initiated by dead start sequence
The dead start sequence forces the exchange address register content to
zero
and also forces a 000 code in the NIP register. These two actions
cause the execution of a
program error exit using memory address zero
as the location of the exchange package. The inactive exchange package
at address zero is then moved into the operating registers and a program
is initiated using these parameters. The exchange package stored at
address zero is largely noise as a result of the dead start operation
and should be discarded by the subsequent entry of new data at these
storage addresses.
Initiated by interrupt flag set
An exchange sequence can be initiated by setting anyone of the nine
interrupt flags in the F register. One or more flags set result in a
request
interrupt signal which initiates an exchange sequence.
Initiated by program exit
There are two program exit instructions that cause the initiation of an
exchange sequence. The timing of the instruction execution (50 CPs) is
the same in either case and consists of an exchange sequence and a fetch
operation.
They differ only in which of the two flags in the F register
is set. The two instructions are:
Program code 000 - Error exit
Program code 004 - Normal exit
2240004
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