Halt (.) - RCA 301 Programmer's Reference Manual

Operation of the Simultaneous Mode
The following instructions are designed to operate in the Simultaneous Mode:
Card Read Simultaneous
Card Punch Simultaneous
Tape Read Forward Simultaneous
Tape Read Reverse Simultaneous
Tape Write Simultaneous
Print and Paper Advance Simultaneous
Block Read Record Simultaneous
Block Write Record Simultaneous
Sector Read Disc Simultaneous
Sector Write Disc Simultaneous
All instructions in the RCA 301 System are staticized in the Normal Mode. When any one of the above instruc­
tions is staticized, provided:
1. SMDI is not on,
2. The system is equipped with a Simultaneous Mode Control Unit, and it is free; i.e., some other instruction
is not now progressing in the Simultaneous Mode,
then the simultaneous instruction is transferred to the Simultaneous Mode; i.e., the contents of the NOR Register
are transferred to SOR, the contents of the N Register are transferred to the M Register, the contents of the A Register
are transferred to the S Register, and the contents of the B Register are transferred to the T Register. The instruction
is then executed in the Simultaneous Mode with SOR, M, S and T Registers acting as the NOR, N, A and B Registers
respectively. The instruction is then processed similarly to a normal instruction. Immediately upon the transfer of
an instruction from the Normal to the Simultaneous Mode, the Normal Mode is free to accept the next instruction.
If a simultaneous instruction is staticized and SMDI is on, the instruction is not transferred to the Simultaneous
Mode, but is executed in the Normal Mode.
If a simultaneous instruction is staticized and SMDI is not on, but the system is not equipped with a Simultaneous
Mode Control Unit, the instruction will be skipped.
If a simultaneous instruction is staticized and SMDI is not on, but the Simultaneous Mode is occupied, the
simultaneous instruction will hold off in the Normal Mode until the Simultaneous Mode is free; i.e., the simultaneous
instruction will occupy the Normal Mode, but will not be executed therein. When the Simultaneous Mode becomes
free, the instruction will be transferred to the Simultaneous Mode to be executed there, freeing the Normal Mode for
the next instruction.
All instructions will be executed serially and will take place in the mode desired when,
1. A System is equipped with a Simultaneous Mode Control Unit.
2. SMDI is not on.
3. ISIM (Inhibit Simultaneity) button on the Console Panel is on.
If a parity error occurs while a Simultaneous Mode input/output instruction is being executed, the mode in which
the error occurred is stopped immediately and the instructions presently being executed in the other modes are
completed before the computer halts. If the error occurs in the Simultaneous Mode, the SAL (Simultaneous Alarm)
light will be on as well as another error light which will indicate the type of error.
Operation of the Data Record File Mode
The following instructions are designed to operate in the Record File Mode:
Record File Mode Read
Record File Mode Write
All instructions are staticized in the Normal Mode. When any one of the above instructions is staticized, provided
the system is equipped with a Record File Mode Control Unit, and it is free (i.e., some other instruction is not
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