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This emulates the classic LINC. The design was settled in 1965, increasing memory to 2048 words, and adding a Z register, an overflow flag, and an interrupt facility.
136 lines
4.5 KiB
Markdown
136 lines
4.5 KiB
Markdown
# LINC emulator
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This is an emulator for the classic LINC from 1965.
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### Devices
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- CPU - LINC processor. If throttled to 125k, approximately original speed.
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- CRT - CRT display. It can be disabled to run headless.
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- DPY - point-plotting display controller.
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- KBD - keyboard. Input comes from typing in the CRT window.
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- SAM - sampled analog inputs.
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- TAPE - four tape drives.
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- TTY - teletype.
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### LOAD
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Software can be loaded into memory using the `LOAD` command. It will
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normally read a file with 16-bit little endian words; the most
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significant four bits of each word should be zero. If the `-O` switch
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is supplied, the input is a text file with octal numbers separated by
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whitespace.
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To start reading from some particular position in the input file, add
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`OFFSET=` after the file name and supply a number in octal.
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To specify where in the memory to put the data, add `START=` after the
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file name; the default is 0. To specify how many words to load, use
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`LENGTH=`; the default is to write until the end of memory.
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A binary input file can be a tape image. A plain image is 512 blocks
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of 256 words each, totalling 262144 bytes. If the `-E` switch is
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used, there is a check for the extended image format that can have
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empty guard blocks at the beginning and the end. The last three words
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in the extended format specify the block size, first forward block
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number, and first reverse block number.
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To state which tape block to start reading, add `BLOCK=` after the
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file name and supply an octal number in the range 0-777.
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### DO
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The SIMH `DO` command has been modified. With arguments, it will
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execute a script file as normal. Without argument, it acts like the
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DO button on the LINC control panel. This executes one instruction
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from the left switches, with the right switches providing a second
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word if needed.
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### Tape drives
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To mount a tape image *file* on drive *n*, type `ATTACH TAPE<n>
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<file>`. The plain or extended image format will be detected
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automatically. Tape drives are numbered 0, 1, 4, and 5.
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The `BOOT TAPEn` command will act like entering a tape read command in
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the switches and starting the computer. The default is to read eight
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blocks starting at 300, and start from location 20. This is the
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conventional way to run LAP6. You can also add `RDC=` or `RCG=` to
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boot some particular blocks. `START=` can be used to specify the
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start address; it defaults to 20.
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### Keyboard
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The keys `0-9`, `A-Z`, and `Space` are mapped to their corresponding
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LINC keys. `Enter` is mapped to `EOL`, `Delete` and `Backspace` are
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mapped to `DEL`, and `Shift` is mapped to `CASE`. To type an upper
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case symbol on some key, press `CASE`, release it, and then type the
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key. For convenience, `Alt` is mapped to `META`.
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The remaining keys are mapped thusly:
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- `F1` is mapped to the `pu` key.
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- `=` is mapped to the `i=` key.
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- `-` and `,` are mapped to the `-,` key.
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- `.` is mapped to the `+. key.
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- `\` is mapped to the `|⊟` key.
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- `[` and `left backslash` are mapped to the `*[` key.
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The remaining upper case symbols:
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- `CASE A` - `"`.
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- `CASE B` - `„`.
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- `CASE C` - `<`.
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- `CASE D` - `>`.
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- `CASE E` - `]`.
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- `CASE F` - `*`.
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- `CASE G` - `:`.
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- `CASE Space` - `?`.
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### Teletype
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The TTY device implmenents a teletype for printing output. When a
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file is attached, it will receive text decoded at 110 baud from relay
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output 0.
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Some characters are translated by LAP6 from the LINC character to ASCII:
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- `i` to `&`
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- `p` to `'`
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- `|` to `\`
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- `u` to `%`
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- `⊟` to `$`
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- `_` to `@`
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- `"` to `^`
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- `„` to `;`
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### CPU
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Registers:
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- P - Instruction location, 10 bits.
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- C - Current instruction, 12 bits.
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- S - Memory address, 12 bits - 11 for address, 1 for halfword select.
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- B - Memory data buffer, 12 bits.
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- A - Accumulator, 12 bits - one's complement.
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- Z - Various, 12 bits.
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- L - Link, 1 bit.
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- OVF - Overflow, 1 bit.
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- IBZ - Tape interblock zone, 1 bit.
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- ENI - Interrupt enabled, 1 bit.
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- PINFF - Pause Interrupt enabled, 1 bit.
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Switches:
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- LSW - Left switches, 12 bits.
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- RSW - Right switches, 12 bits.
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- SSW - Sense switches, 6 bits.
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Inputs:
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- INTREQ, Interrupt request, 1 bit.
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- R - Relays, 6 bits.
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- XL - External levels, 12 of 1 bit each.
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- SAM - Sampled analog inputs, 16 of 8 bits each; one's complement.
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### Documentation
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Programming:
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https://bitsavers.org/pdf/washingtonUniversity/linc/Programming_the_LINC_Second_Edition_Jan69.pdf
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Using the LAP6 operating system, text editor, assembler, tape filing system:
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https://bitsavers.org/pdf/washingtonUniversity/linc/LINC_Reference_Manuals/LINC_Vol_16_Section_3_LAP6_Handbook_May67.pdf
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