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analogs. They are functionally equivalent to presetting or power-cycling just the specified device and its associated
interface card.
2.2.6 RUN and GO
The RUN and GO commands accept only logical addresses consisting of 15-bit offsets within the 32K logical
address space (e.g., 77777). If the starting address is supplied, it is stored in the P register before execution
begins. Otherwise, execution begins at the current P-register location.
The RUN command does an implied RESET, so it is equivalent in hardware to pressing the front-panel PRESET
and RUN buttons on the CPU. As PRESET initializes all of the I/O interfaces, the RUN command is almost never
the proper command to use after a program has been started. The GO command is equivalent to pressing the
RUN button on the CPU and is the usual way of resuming execution after a programmed halt. If a PRESET is
required before resuming, the RESET and GO commands are direct analogs of pressing the PRESET and RUN
buttons, respectively.
2.2.7 LOAD, DUMP, and BOOT
The LOAD command is used to install a 64-word bootstrap loader from an absolute binary file. The syntax is:
LOAD <image-filename> {<select-code>}
The file is read into the last 64 words of memory. If the optional select code is supplied, the loader I/O instructions
are configured to the specified device; otherwise, the loader is not modified. If the CPU is configured as a 2114,
2115, 2116, or 2100, then when the command completes, the loader remains unprotected so that it may be
executed. The loader should be protected with a SET CPU LOADERDISABLE command if it will not be used
immediately.
The binary file must be targeted to addresses in the octal range x7700-x7777, where x is 0-7. The loaded program
will be relocated to the last 64 words of memory, so the desired memory size must be set before issuing the LOAD
command. If the optional configuration select code is supplied, all I/O instructions in the program that reference
select codes >= 10 octal will be changed by adding the supplied value minus 10 to the instruction. The effect of this
is that instructions that reference select code 10 + n will be changed to reference the supplied select code + n. This
permits the configuration of loaders using two-card interfaces that reference select codes 10 and 11.
For 1000-series CPUs, the LOAD command serves to install boot loader ROM images other than the ones included
with the device simulators. If the CPU is configured with more than 32K of memory, the loader is installed in the
last 64 words of the 32K logical address space.
The DUMP command writes the bootstrap loader currently residing in memory to an absolute binary file. The
command format is:
DUMP <image-filename>
For 21xx CPUs, the loader must be unprotected with a SET CPU LOADERENABLE command before entering the
DUMP command; if the loader is protected, the output file will contain all zeros. When the command completes,
the loader remains unprotected. The resulting file may be used in a subsequent LOAD command to reload the
bootstrap program.
The CPU supports the BOOT command. It is the hardware equivalent of pressing IBL, PRESET, and RUN on the
front panel. The S register must be set to the appropriate value to specify the desired boot loader ROM and device
select code before entering the command.
Bootable peripherals, such as the tape and disc drives, also implement the BOOT command. Entering a BOOT
command for one of these devices will preset the S register to the appropriate value before loading and executing
the applicable initial binary loader. The bootstrap loaders support booting only from unit 0 of the target device.
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